Guiding anti-tachyarrhythmia pacing train design and electrode selection with electrograms

ABSTRACT

An example medical device system includes therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry. The ATP therapy includes one or more ATP trains. The medical device system also includes processing circuitry configured determine a first propagation time based on a comparison of features in a local electrogram and a far-field electrogram, such as the time from a fiducial point in the local electrogram and QRS onset in the far-field electrogram. The processing circuitry is also configured to determine, based on the first propagation time, a number of pulses to achieve a second propagation time and control the therapy delivery circuitry to deliver the ATP train of at least the number of pulses.

This application claims the benefit of U.S. Provisional Application No. 63/117,574, filed Nov. 24, 2020, and entitled “GUIDING ANTI-TACHYARRHYTHMIA PACING TRAIN DESIGN AND ELECTRODE SELECTION WITH ELECTROGRAMS,” the entire content of which is incorporated by reference herein.

TECHNICAL FIELD

The disclosure relates to medical devices, and, more particularly, to medical device systems configured to detect and treat cardiac arrhythmias with anti-tachyarrhythmia pacing (ATP) therapy.

BACKGROUND

Implantable cardioverter defibrillators (ICDs) and implantable artificial pacemakers may provide cardiac pacing therapy to a patient's heart when the natural pacemaker and/or conduction system of the heart fails to provide synchronized atrial and ventricular contractions at rates and intervals sufficient to sustain healthy patient function. Such antibradycardial pacing may provide relief from symptoms, or even life support, for a patient. Cardiac pacing may also provide electrical overdrive stimulation, e.g., ATP therapy, to suppress or convert tachyarrhythmias, again supplying relief from symptoms and preventing or terminating arrhythmias that could lead to sudden cardiac death.

SUMMARY

ATP therapy may be delivered to advance the heart to refractory thereby terminating a tachyarrhythmia. Some medical device systems that may deliver ATP therapy that includes delivering a first ATP train of a set predetermined length. This set predetermined length may be a length that may be therapeutic to a large number of patients. However, the set predetermined length of the ATP train may be too long for some patients and too short for other patients. An ATP train that is too long may accelerate ventricular tachyarrhythmia (VT) into ventricular fibrillation (VF). An ATP train that is too short may be a wasted train, since it did not terminate the tachyarrhythmia, and may decrease the amount of time available to correct the VT.

The systems and methods described herein may be used to determine a length of an ATP train that may vary between different patients. In some examples, the ATP train may be the first train delivered by the implantable device during a VT event. These techniques may be used to improve the efficacy of ATP therapy.

In one example, this disclosure is directed to a method including determining, by a medical device system, a first feature in a local electrogram; determining, by the medical device system, a second feature in a far-field electrogram; determining, by the medical device system, a first propagation time based on the first feature and the second feature; determining, by the medical device system and based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and delivering, by the medical device system, the ATP train of at least the number of pulses.

In another example, this disclosure is directed to a method including pacing, by a first electrode, a heart of a patient; determining, by a medical device system, a first feature in a local electrogram in response to the pace; determining, by the medical device system and for each electrode of a plurality of other electrodes communicatively coupled to a medical device, a respective second feature in a respective electrogram; determining, by the medical device system, and for each of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the respective second feature onset; comparing, by the medical device system, the respective propagation times associated with each of the plurality of other electrodes; determining, by the medical device system and based on the comparison, an electrode associated with a shortest respective propagation time; selecting, by the medical device system, the electrode associated with the shortest respective propagation time for delivery of anti-tachycardia pacing (ATP) therapy; and delivering, by the medical device system and via the selected electrode, the ATP therapy.

In another example, this disclosure is directed to medical device system including therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry, the ATP therapy comprising an ATP train; and processing circuitry configured to: determine a first feature in a local electrogram; determine a second feature in a far-field electrogram; determine a first propagation time based on the first feature and the second feature; determine a number of pulses of the ATP train to achieve a second propagation time based on the first propagation time; and control the therapy delivery circuitry to deliver the ATP train of at least the number of pulses.

In another example, this disclosure is directed to medical device system including therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry; and processing circuitry configured to: control a first electrode to pace a heart of a patient; determine a first feature in a local electrogram in response to the pace; determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective second feature in a respective electrogram; determine, for each of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the respective second feature; compare the respective propagation times associated with each of the plurality of other electrodes; determine, based on the comparison, an electrode associated with a shortest respective propagation time; select the electrode associated with the shortest respective propagation time for delivery of the ATP therapy; and control the therapy delivery circuitry to deliver the ATP therapy via the selected electrode.

In a further example, this disclosure is directed to a non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause processing circuitry to: determine a first feature in a local electrogram; determine a second feature in a far-field electrogram; determine a first propagation time based on the first feature and the second feature; determine, based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and control therapy delivery circuitry to deliver the ATP train of the at least the number of pulses.

In a further example, this disclosure is directed to a non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause processing circuitry to: determine a first feature in a local electrogram; determine, for each electrode of a plurality of other electrodes communicatively coupled to a medical device system, a respective second feature in a respective electrogram; determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the second feature; compare the respective propagation times associated with each of a plurality of other electrodes; determine, based on the comparison, an electrode associated with a shortest respective propagation time; select the electrode associated with the shortest respective propagation time for delivery of anti-tachycardia pacing (ATP) therapy; and control therapy delivery circuitry to deliver the ATP therapy via the selected electrode.

This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail within the accompanying drawings and description below. The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a front view of a patient implanted with an example implantable medical device system.

FIG. 1B is a side view of the patient implanted with the implantable medical device system of FIG. 1A.

FIG. 1C is a transverse view the patient implanted with the implantable medical device system of FIGS. 1A and 1B.

FIG. 2 is a conceptual drawing illustrating an example configuration of the intracardiovascular pacing device (IPD) of the implantable medical device system of FIGS. 1A-1C.

FIG. 3 is a schematic diagram of another example implantable medical device system in conjunction with a patient.

FIG. 4 is a conceptual drawing illustrating an example configuration of the insertable cardiac monitor (ICM) of the implantable medical device system of FIG. 3.

FIG. 5 is a functional block diagram illustrating an example configuration of the IPD of FIGS. 1A-1C and 2.

FIG. 6 is a functional block diagram illustrating an example configuration of the ICD of the implantable medical device system of FIGS. 1A-1C.

FIG. 7 is a functional block diagram illustrating an example configuration of the external device of FIGS. 1A-1C and FIG. 3.

FIG. 8 is a functional block diagram illustrating an example configuration of the pacemaker/cardioverter/defibrillator (PCD) of the implantable medical device system of FIG. 3.

FIG. 9 is a functional block diagram illustrating an example configuration of the ICM of FIGS. 1A-1C and FIG. 4.

FIGS. 10A-10C are conceptual diagrams illustrating example local electrograms and far-field electrograms according to the techniques of this disclosure.

FIG. 11 is a conceptual diagram illustrating an ATP train.

FIG. 12 is a flowchart illustrating an example technique for determining a length of an ATP train according to this disclosure.

FIG. 13 is a flowchart illustrating an example technique for determining an electrode to deliver ATP therapy according to this disclosure.

DETAILED DESCRIPTION

FIGS. 1A-1C are conceptual diagrams illustrating various views of an example implantable medical device system 8. The system 8 includes an extracardiovascular ICD system 6, including ICD 9 connected to a medical electrical lead 10, and IPD 16 configured in accordance with the principles of the present application. FIG. 1A is a front view of a patient 14 implanted with the medical device system 8. FIG. 1B is a side view of patient 14 implanted with the medical device system 8. FIG. 1C is a transverse view of patient 14 implanted with the medical device system 8.

The ICD 9 may include a housing that forms a hermetic seal that protects components of the ICD 9. The housing of the ICD 9 may be formed of a conductive material, such as titanium or titanium alloy, which may function as a housing electrode (sometimes referred to as a can electrode). In other examples, the ICD 9 may be formed to have or may include one or more electrodes on the outermost portion of the housing. The ICD 9 may also include a connector assembly (also referred to as a connector block or header) that includes electrical feedthroughs through which electrical connections are made between conductors of lead 10 and electronic components included within the housing of the ICD 9. As will be described in further detail herein, housing may house one or more processors, memories, transmitters, receivers, sensors, sensing circuitry, therapy delivery circuitry, power sources and other appropriate components. The housing is configured to be implanted in a patient, such as patient 14.

ICD 9 is implanted extra-thoracically on the left side of patient 14, e.g., under the skin and outside the ribcage (subcutaneously or submuscularly). ICD 9 may, in some instances, be implanted between the left posterior axillary line and the left anterior axillary line of patient 14. ICD 9 may, however, be implanted at other extra-thoracic locations on patient 14 as described later.

Lead 10 may include an elongated lead body 12 sized to be implanted in an extracardiovascular location proximate the heart, e.g., intra-thoracically (as illustrated in FIGS. 1A-C), subcutaneously, or intercostally for example. In the illustrated example, lead body 12 extends superiorly intra-thoracically underneath the sternum, in a direction substantially parallel to the sternum. In one example, the distal portion 24 of lead 10 may reside in a substernal location such distal portion 24 of lead 10 extends superior along the posterior side of the sternum substantially within the anterior mediastinum 36. Anterior mediastinum 36 may be viewed as being bounded laterally by pleurae 39, posteriorly by pericardium 38, and anteriorly by the sternum 22. In some instances, the anterior wall of anterior mediastinum 36 may also be formed by the transversus thoracis and one or more costal cartilages. Anterior mediastinum 36 includes a quantity of loose connective tissue (such as areolar tissue), adipose tissue, some lymph vessels, lymph glands, substernal musculature (e.g., transverse thoracic muscle), the thymus gland, branches of the internal thoracic artery, and the internal thoracic vein. Lead 10 may be implanted at other locations, such as over the sternum, offset to the right of the sternum, angled lateral from the proximal or distal end of the sternum, or the like. In other examples, distal portion of lead 10 may reside within a blood vessel within the substernal location, such as within an internal thoracic artery, an internal thoracic vein, an intercostal vein, the superior epigastric vein, or the azygos, hemiazygos, or accessory hemiazygos veins, as examples. In this manner, lead 10 remains outside the heart in an extra-cardiac location.

Lead body 12 may have a generally tubular or cylindrical shape and may define a diameter of approximately 3-9 French (Fr), however, lead bodies of less than 3 Fr and more than 9 Fr may also be utilized. In another configuration, lead body 12 may have a flat, ribbon, or paddle shape with solid, woven filament, or metal mesh structure, along at least a portion of the length of lead body 12. In such an example, the width across lead body 12 may be between 1-3.5 mm. Other lead body designs may be used without departing from the scope of this application.

Lead body 12 of lead 10 may be formed from a non-conductive material, including silicone, polyurethane, fluoropolymers, mixtures thereof, and other appropriate materials, and shaped to form one or more lumens (not shown), however, the techniques are not limited to such constructions. Distal portion 24 may be fabricated to be biased in a desired configuration, or alternatively, may be manipulated by the user into the desired configuration. For example, distal portion 24 may be composed of a malleable material such that the user can manipulate distal portion 24 into a desired configuration where it remains until manipulated to a different configuration. However, distal portion 24 may take on different configurations, including a straight configuration, circular configuration or any of a number of configurations.

Lead body 12 may include a proximal end 14 and a distal portion 24 configured to deliver electrical energy to the heart or sense electrical energy of the heart. Distal portion 24 may be anchored to a desired positioned within the patient, for example, substernally or subcutaneously by, for example, suturing distal portion 24 to the patient's musculature, tissue, or bone at the xiphoid process entry site. Alternatively, distal portion 24 may be anchored to the patient or through the use of rigid tines, prongs, barbs, clips, screws, and/or other projecting elements or flanges, disks, pliant tines, flaps, porous structures such as a mesh-like element and metallic or non-metallic scaffolds that facilitate tissue growth for engagement, bio-adhesive surfaces, and/or any other non-piercing elements.

Distal portion 24 includes defibrillation electrode 28 configured to deliver a cardioversion/defibrillation shock to the patient's heart. Defibrillation electrode 28 may include a plurality of sections or segments 28 a and 28 b spaced a distance apart from each other along the length of distal portion 24. The defibrillation electrode segments 28 a and 28 b may be a disposed around or within lead body 12 of distal portion 24, or alternatively, may be embedded within the wall of lead body 12. In one configuration, defibrillation electrode segments 28 a and 28 b may each be a coil electrode formed by a conductor. The conductor may be formed of one or more conductive polymers, ceramics, metal-polymer composites, semiconductors, metals or metal alloys, including but not limited to, one of or a combination of the platinum, tantalum, titanium, niobium, zirconium, ruthenium, indium, gold, palladium, iron, zinc, silver, nickel, aluminum, molybdenum, stainless steel, MP35N, carbon, copper, polyaniline, polypyrrole and other polymers. In another configuration, each of the defibrillation electrodes segments 28 a and 28 b may be a flat ribbon electrode, a paddle electrode, a braided or woven electrode, a mesh electrode, a directional electrode, a patch electrode or another type of electrode configured to deliver a cardioversion/defibrillation shock to the patient's heart.

In one configuration, the defibrillation electrode segments 28 a and 28 b are spaced approximately 0.25-4.5 cm, and in some instances between 1-3 cm apart from each other. In another configuration, the defibrillation electrode segments 28 a and 28 b are spaced approximately 0.25-1.5 cm apart from each other. In a further configuration, the defibrillation electrode segments 28 a and 28 b are spaced approximately 1.5-4.5 cm apart from each other. In the configuration shown in FIGS. 1A-1C, the defibrillation electrode segments 28 a and 28 b span a substantial part of distal portion 24. Each of the defibrillation electrode segments 28 a and 28 b may be between approximately 1-10 cm in length and, more preferably, between 2-6 cm in length and, even more preferably, between 3-5 cm in length. However, lengths of greater than 10 cm and less than 1 cm may be utilized without departing from the scope of this disclosure. A total length of defibrillation electrode 28 (e.g., length of the two segments 28 a and 28 b combined) may vary depending on a number of variables. The defibrillation electrode 28 may, in one example, have a total length of between approximately 5-10 cm. However, the defibrillation electrode segments 28 a and 28 b may have a total length less than 5 cm and greater than 10 cm in other examples. In some instances, defibrillation segments 28 a and 28 b may be approximately the same length or, alternatively, different lengths.

The defibrillation electrode segments 28 a and 28 b may be electrically connected to one or more conductors, which may be disposed in the body wall of lead body 12 or may alternatively be disposed in one or more insulated lumens (not shown) defined by lead body 12. In an example configuration, each of the defibrillation electrode segments 28 a and 28 b is connected to a common conductor such that a voltage may be applied simultaneously to all the defibrillation electrode segments 28 a and 28 b to deliver a defibrillation shock to a patient's heart. In other configurations, the defibrillation electrode segments 28 a and 28 b may be attached to separate conductors such that each defibrillation electrode segment 28 a or 28 b may apply a voltage independent of the other defibrillation electrode segments 28 a or 28 b. In this case, ICD 9 or lead 10 may include one or more switches or other mechanisms to electrically connect the defibrillation electrode segments together to function as a common polarity electrode such that a voltage may be applied simultaneously to all the defibrillation electrode segments 28 a and 28 b in addition to being able to independently apply a voltage.

In one example, the distance between the closest defibrillation electrode segment 28 a and 28 b and electrodes 32 a and 32 b is greater than or equal to 2 mm and less than or equal to 1.5 cm. In another example, electrodes 32 a and 32 b may be spaced apart from the closest one of defibrillation electrode segments 28 a and 28 b by greater than or equal to 5 mm and less than or equal to 1 cm. In a further example, electrodes 32 a and 32 b may be spaced apart from the closest one of defibrillation electrode segments 28 a and 28 b by greater than or equal to 6 mm and less than or equal to 8 mm.

Electrodes 32 a and 32 b may be configured to deliver low-voltage electrical pulses to the heart and/or may sense a cardiac electrical activity, e.g., depolarization and repolarization of the heart. As such, electrodes 32 a and 32 b may be referred to herein as pace/sense electrodes 32 a and 32 b. In one configuration, electrodes 32 a and 32 b are ring electrodes. However, in other configurations the electrodes 32 a and 32 b may be any of a number of different types of electrodes, including ring electrodes, short coil electrodes, paddle electrodes, hemispherical electrodes, directional electrodes, or the like. Electrodes 32 a and 32 b may be the same or different types of electrodes. Electrodes 32 a and 32 b may be electrically isolated from an adjacent defibrillation segment 28 a or 28 b by including an electrically insulating layer of material between electrodes 32 a and 32 b and the adjacent defibrillation segments 28 a and 28 b. Each electrode 32 a or 32 b may have its own separate conductor such that a voltage may be applied to each electrode independently from another electrode 32 a or 32 b in distal portion 24. In other configurations, each electrode 32 a or 32 b may be coupled to a common conductor such that each electrode 32 a or 32 b may apply a voltage simultaneously.

Proximal end 14 of lead body 12 may include one or more connectors 34 to electrically couple lead 10 to the implantable cardioverter-defibrillator (ICD) 9 subcutaneously implanted within the patient, for example, under the left armpit of the patient. The ICD 9 may include a housing 38 that forms a hermetic seal which protects the components of ICD 9. The housing of ICD 9 may be formed of a conductive material, such as titanium or titanium alloy, which may function as a housing electrode for a particular therapy vector between the housing and distal portion 24. ICD 9 may also include a connector assembly that includes electrical feedthroughs through which electrical connections are made between the one or more connectors 34 of lead 10 and the electronic components included within the housing. The housing of ICD 9 may house one or more processors, memories, transmitters, receivers, sensors, sensing circuitry, therapy circuitry, power sources (capacitors and batteries) and/or other appropriate components. The components of ICD 9 may generate and deliver electrical stimulation therapy such as ATP.

The inclusion of electrodes 32 a and 32 b adjacent to defibrillation electrode segments 28 a and 28 b provides a number of therapy vectors for the delivery of electrical stimulation therapy to the heart. For example, as shown in FIGS. 1A-1C, at least a portion of the defibrillation electrode 26 and one of the electrodes 32 a and 32 b may be disposed over the right ventricle, or any chamber of the heart, such that pacing pulses and defibrillation shocks may be delivered to the heart. The housing of ICD 9 may be charged with or function as a polarity different than the polarity of the one or more defibrillation electrode segments 28 a and 28 b and/or electrodes 32 a and 32 b such that electrical energy may be delivered between the housing and the defibrillation electrode segment(s) 28 a and 28 b and/or electrode(s) 32 a and 32 b to the heart. Each defibrillation electrode segment 28 a or 28 b may have the same polarity as every other defibrillation electrode segment 28 a or 28 b when a voltage is applied to it such that a defibrillation shock may be delivered from the entirety of the defibrillation electrode 28. In examples in which defibrillation electrode segments 28 a and 28 b are electrically connected to a common conductor within lead body 12, this is the only configuration of defibrillation electrode segments 28 a and 28 b. However, in other examples, defibrillation electrode segments 28 a and 28 b may be coupled to separate conductors within lead body 12 and may therefore each have different polarities such that electrical energy may flow between defibrillation electrode segments 28 a and 28 b (or between one of defibrillation electrode segments 28 a and 28 b and one or more pace/sense electrodes 32 a and 32 b or the housing electrode) to provide pacing therapy and/or to sense cardiac depolarizations. In this case, the defibrillation electrode segments 28 a and 28 b may still be electrically coupled together (e.g., via one or more switches within ICD 9) to have the same polarity to deliver a defibrillation shock from the entirety of the defibrillation electrode 28.

Additionally, each electrode 32 a and 32 b may be configured to conduct electrical pulses directly to the heart, or sense a cardiac depolarization between adjacent defibrillation electrode segments 28 a and 28 b, whether disposed on the same defibrillation electrode segment 28 a or 28 b or on other defibrillation electrode segment 28 a or 28 b, and/or between proximate electrodes 32 a and 32 b. Additionally electrodes 32 a and 32 b may conduct electrical pulses between one another, e.g., between one of electrodes 32 a and 32 b and an inferior and superior electrode 32 a and 32 b, between one of electrodes 32 a and 32 b and the housing electrode, or between a plurality of electrodes 32 a and 32 b (at the same polarity) and the housing electrode at the opposite polarity. As such, each electrode 32 a or 32 b may have the same polarity as every other electrode 32 a or 32 b or alternatively, may have different polarities such that different therapy vectors can be utilized to deliver pacing pulses to the heart.

IPD 16 may be implanted within a heart 26 of patient 14. In the example of FIGS. 1A-1C, IPD 16 is implanted within right ventricle of heart 26 to sense electrical activity of heart 26 and deliver pacing therapy, e.g., ATP therapy, to heart 26. IPD 16 may be attached to an interior wall of the right ventricle of heart 26 via one or more fixation elements that penetrate the tissue. These fixation elements may secure IPD 16 to the cardiac tissue and retain an electrode (e.g., a cathode or an anode) in contact with the cardiac tissue. However, in other examples, system 8 may include additional pacing devices 16 within respective chambers of heart 26 (e.g., right or left atrium and/or left ventricle). In further examples, a cardiac pacing device configured similarly to IPD 16 may be attached to an external surface of heart 26 (e.g., in contact with the epicardium) such that the pacing device is disposed outside of heart 26.

IPD 16 may be capable sensing electrical signals using the electrodes carried on the housing of IPD 16. These electrical signals may be electrical signals generated by cardiac muscle and indicative of depolarizations and repolarizations of heart 26 at various times during the cardiac cycle. IPD 16 may analyze the sensed electrical signals to detect tachyarrhythmias, such as ventricular tachycardia or ventricular fibrillation. In response to detecting the tachyarrhythmia, IPD 16 may, e.g., depending on the type of tachyarrhythmia, begin to deliver ATP therapy via the electrodes of IPD 16.

In some examples, IPD 16 and ICD 9 may be configured to communicate with one another, e.g., via radio-frequency communication, conductive or galvanic communication or other type of communication, to cooperate with one another. For example, IPD 16 and ICD 9 may communicate information, such as sense signals and/or delivered signals, and may coordinate to establish pacing and/or sensing vectors between respective electrodes on ICD 9, IPD 16, and/or lead 10. IPD 16 and ICD 9 may be configured for one-way or two-way communication.

In other examples, IPD 16 and ICD 9 are not configured to communicate with each other. In such examples, each of IPD 16 and ICD 9 may independently monitor the electrical activity of heart, and deliver therapy in response to detecting arrhythmia. In such examples, one or both of IPD 16 and ICD 9 may be configured to detect activity of, e.g., delivery of therapy by, the other. In this manner, delivery of therapies by IPD 16 and ICD 9 may be coordinated without conventional uni- or bi-directional communication between the devices.

In some examples, a medical system according to the techniques of this disclosure may include one device, such as ICD 9, and may not include an IPD.

An implantable medical device, such as IPD 16 or ICD 9 that delivers anti-tachyarrhythmia pacing (ATP) therapy may use a first pacing train of a predetermined number of pulses. The predetermined number of pulses of ATP train length may be based on an estimation of how much propagation time is needed to interact with ventricular tachycardia (VT) in a patient. This predetermined number of pulses of an ATP train may be a number of pulses selected to address a large portion of the population having irregular heartbeats. As an example, this predetermined number of pulses of an ATP train may be determined such that the predetermined number of pulses corresponds to a propagation time of 150 ms. For example, a number of pulses of an ATP train that achieves a propagation of 150 ms may be of sufficient enough to interact with VT for nearly 97% of patients. A first ATP train of such a number of pulses may be wasted on the other 3%. of patients, as the number of pulses may not be great enough to interact with VT for those 3% of patients. In some examples, a number of pulses of an ATP train sufficient to achieve a propagation of length of 70 ms may be sufficient enough to interact with VT for around 50% of patients. In these cases, a number of pulses of an ATP train that achieves a propagation delay of 150 ms may be longer than necessary. In some instances, ATP trains with a high number of pulses at rapid rates may drive more issues with acceleration of the VT into ventricular fibrillation (VF).

According to the techniques of this disclosure, rather than use a predetermined number of pulses of an ATP train, an implantable medical device, or processing circuitry of other devices in a medical device system including the implantable medical device, may determine a number of pulses ATP train length based on a propagation time from a first feature (e.g., a fiducial point) in a local electrogram, such as an ATP electrode electrogram activation (peak or max dV/dt), to a second feature (e.g., an onset of a QRS complex, also described herein as a QRS onset) in a far-field electrogram. For example, a local electrogram may be an electrogram from a pair of electrodes in which at least one of the pair of electrodes is also used for stimulation during ATP, or is within about 1 cm of an electrode used for delivering ATP or is within about 1 cm to any tissue directly captured by an electrode used in the delivery of ATP. For example, a far-field electrogram is an electrogram such as a can-coil, coil-coil, or event tip-can electrode configuration, where at least one of the electrodes is not in contact with the ventricles and is sensitive to a larger region of the ventricles.

In some examples, a fiducial point may be an activation point, such as in a bipolar electrogram, a peak amplitude. In other examples, a fiducial point may be a largest negative slope (min dV/dt), such as in a unipolar example. Although primarily described herein as implantable, the ATP delivering device of this disclosure could be an external device, such as an external pacemaker or wearable automated external defibrillator (AED).

While the techniques of this disclosure may be discussed with respect to specific devices, in some examples, the techniques of this disclosure may be performed by a combination of devices, rather than a single device. For example, one device may determine the first feature in the local electrogram, while another device(s) may determine the second feature in the far-field electrogram. In some examples, one device may determine both the first feature in the local electrogram and determine the second feature in the far-field electrogram, whether or not the device has local electrodes or far-field electrodes. For example, processing circuitry of one or more devices may make the determinations based on signals sensed by electrodes coupled to the one or more devices or coupled to other devices. For example, processing circuitry of one or more devices may cooperate to perform any of the techniques of this disclosure. In some examples, processing circuitry of external device 21 may perform the techniques of this disclosure or may cooperate with processing circuitry of one or more other devices to perform the techniques of this disclosure.

In some examples, the medical device system may determine a number of pulses of the ATP train based on which range, from a plurality of ranges of first propagation times, the first propagation time being associated with a first feature in a local electrogram and a second feature in a far-field electrogram. For example, a number of ranges of first propagation times may be stored in memory on the medical device system and the medical device system may select a specific number of pulses of an ATP train to achieve a second propagation time based on which range is associated with the first propagation time.

The following discussion provides examples of a range-based approach to determining a number of pulses of an ATP train and should not be considered limiting. In some examples, a medical device system may store 3 ranges of first propagation times in memory. A first range may include propagation times of less than 10 ms. A medical device system may determine a number of pulses of ATP train length to achieve a second propagation time of 100 ms based on the first propagation time falling within this first range of less than 10 ms. A second range may include propagation times between 10 ms and 40 ms. A medical device system may determine a number of pulses of ATP train length to achieve a second propagation time of 150 ms based on the first propagation time falling within this second range of between 10 ms and 40 ms. A third range may include propagation times greater than 40 ms. A medical device system may determine a number of pulses of ATP train length to achieve a second propagation time of 210 ms based on the propagation time falling within this third range of greater than 40 ms.

In some examples, the determination of the number of pulses of the ATP train may not be range-based. For example, a medical device system may apply a formula, a linear equation, or a continuous function to the first propagation time to determine the number of pulses of the ATP train. In some examples, the medical device system may look up the first propagation time in a look-up table, which may provide a number of pulses of the ATP train.

According to the techniques of this disclosure a medical device system, which may include an implantable medical device, such as ICD 9 or IPD 16, may deliver ATP trains of a number of pulses that are more tailored to an individual patient than a medical device system using predetermined number of pulses for ATP trains. For example, using fewer number of pulses for certain patients may more often lower the risk of the ATP accelerating VT. Using a larger number of pulses for certain patients may save a potentially wasted pacing sequence. Avoiding a wasted pacing sequence may improve efficacy for very rapid VTs, as a clinician may only set a limited number of sequences, such as 3, for very rapid VTs, before initiating shock(s).

In some examples, a medical device system may use the same or similar information (e.g., propagation times) to select which pace/sense electrodes should be used to deliver the ATP therapy. For example, the medical device system may select the pace/sense electrodes that have the smallest propagation time. By selecting the pace/sense electrodes with the shortest propagation time, the medical device system may save the need to use test sequences or to select a predetermined or random electrode, start pacing, and then adapt which electrodes are used to pace.

Although FIGS. 1A-1C are described in the context of an ICD 9 connected to lead 10 and IPD 16, the techniques may be applicable to other systems. For example, a medical device that includes a lead having a distal portion that is implanted above the sternum (or other extra-thoracic, subcutaneous location or intercostal location) instead of being implanted below the ribs and/or sternum. As another example, instead of an intracardiac pacing device, a pacing system may be implanted having a subcutaneous or submuscular pacemaker and one or more leads connected to and extending from the pacemaker into one or more chambers of the heart or attached to the outside of the heart to provide pacing therapy to the one or more chambers. As such, the example of FIGS. 1A-1C is illustrated for exemplary purposes only and should not be considered limiting of the techniques described herein.

External device 21 may be configured to communicate with one or both of ICD 9 and IPD 16. In examples where external device 21 only communicates with one of subcutaneous ICD 9 and IPD 16, the non-communicative device may receive instructions from or transmit data to the device in communication with external device 21. In some examples, external device 21 comprises a handheld computing device, computer workstation, or networked computing device. External device 21 may include a user interface that receives input from a user. In other examples, the user may also interact with external device 21 remotely via a networked computing device. The user may interact with external device 21 to communicate with IPD 16 and/or ICD 9. For example, the user may interact with external device 21 to send an interrogation request and retrieve therapy delivery data, update therapy parameters that define therapy, manage communication between IPD 16 and/or ICD 9, or perform any other activities with respect to IPD 16 and/or ICD 9. In some examples, the user is a clinician, such as a physician, technician, surgeon, electrophysiologist, or other healthcare professional. In some examples, the user may be patient 14.

External device 21 may also allow the user to define how IPD 16 and/or ICD 9 senses electrical signals (e.g., electrocardiograms (ECGs)), detects arrhythmias such as tachyarrhythmias, delivers therapy, and communicates with other devices of system 8. For example, external device 21 may be used to change tachyarrhythmia detection parameters. In another example, external device 21 may be used to manage therapy parameters that define therapies such as ATP therapy. Moreover, external device 21 may be used to alter communication protocols between IPD 16 and ICD 9. For example, external device 21 may instruct IPD 16 and/or ICD 9 to switch between one-way and two-way communication and/or change which of IPD 16 and/or ICD 9 are tasked with initial detection of arrhythmias.

External device 21 may communicate with IPD 16 and/or ICD 9 via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, proprietary and non-proprietary radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, external device 21 may include a programming head that may be placed proximate to patient 14's body near the IPD 16 and/or ICD 9 implant site in order to improve the quality or security of communication between IPD 16 and/or ICD 9 and external device 21.

In some examples, IPD 16 and ICD 9 may engage in communication to facilitate the appropriate detection of arrhythmias and/or delivery of anti-tachycardia therapy. Anti-tachycardia therapy may include ATP. The communication may include one-way communication in which one device is configured to transmit communication messages and the other device is configured to receive those messages. The communication may instead include two-way communication in which each device is configured to transmit and receive communication messages. Although the examples below describe detection of tachyarrhythmias and the delivery of ATP, IPD 16 and ICD 9 may be configured to communicate with each other and provide alternative electrical stimulation therapies.

The leads and systems described herein may be used at least partially within the substernal space, e.g., within anterior mediastinum of patient, to provide a medical device system. An implanter (e.g., physician) may implant the distal portion of the lead intrathoracically using any of a number of implant tools, e.g., tunneling rod, sheath, or other tool that can traverse the diagrammatic attachments and form a tunnel in the substernal location. For example, the implanter may create an incision near the center of the torso of the patient, e.g., and introduce the implant tool into the substernal location via the incision. The implant tool is advanced from the incision superior along the posterior of the sternum in the substernal location. The distal end of lead 10 is introduced into tunnel via implant tool (e.g., via a sheath). As the distal end of lead 10 is advanced through the substernal tunnel, the distal end of lead 10 is relatively straight. The preformed or shaped undulating portion is flexible enough to be straightened out while routing the lead 10 through a sheath or other lumen or channel of the implant tool. Once the distal end of lead 10 is in place, the implant tool is withdrawn toward the incision and removed from the body of the patient while leaving lead 10 in place along the substernal path. As the implant tool is withdrawn, the distal end of lead 10 takes on its pre-formed undulating configuration. Thus, as the implant tool is withdrawn, the undulating configuration pushes electrodes 32 a and 32 b toward the left side of sternum compared to electrode segments 28 a and 28 b. As mentioned above, the implanter may align the electrodes 32 a and 32 b along the anterior median line (or midsternal line) or the left sternal lines (or left lateral sternal line).

Although system 8 is illustrated as including both extracardiovascular ICD system 6 and IPD 16, in some examples, a system may include extracardiovascular ICD system 6 without IPD 16. In such examples, ICD system 6 may perform the techniques described herein without the use of IPD 6. In some examples, system 8 may include extracardiovascular ICD system 6 and IPD 16 and extracardiovascular ICD system 6 may, at some times, perform the techniques described herein in coordination with IPD 16 and, at other times, perform the techniques described herein without the use of IPD 16.

FIG. 2 is a conceptual drawing illustrating an example configuration of IPD 16 of the medical device system of FIGS. 1A-1C. As shown in FIG. 2, IPD 16 includes case 50, cap 58, electrode 60, electrode 52, fixation mechanisms 62, flange 54, and opening 56. Together, case 50 and cap 58 may be considered the housing of IPD 16. In this manner, case 50 and cap 58 may enclose and protect the various electrical components within IPD 16. Case 50 may enclose substantially all of the electrical components, and cap 58 may seal case 50 and create the hermetically sealed housing of IPD 16. Although IPD 16 is generally described as including one or more electrodes, IPD 16 may typically include at least two electrodes (e.g., electrodes 52 and 60) to deliver an electrical signal (e.g., therapy such as ATP) and/or provide at least one sensing vector.

Electrodes 52 and 60 are carried on the housing created by case 50 and cap 58. In this manner, electrodes 52 and 60 may be considered leadless electrodes. In the example of FIG. 2, electrode 60 is disposed on the exterior surface of cap 58. Electrode 60 may be a circular electrode positioned to contact cardiac tissue upon implantation. Electrode 52 may be a ring or cylindrical electrode disposed on the exterior surface of case 50. Both case 50 and cap 58 may be electrically insulating. Electrode 60 may be used as a cathode and electrode 52 may be used as an anode, or vice versa, for delivering pacing stimulation therapy such as ATP. However, electrodes 52 and 60 may be used in any stimulation configuration. In addition, electrodes 52 and 60 may be used to detect intrinsic electrical signals from cardiac muscle. In other examples, IPD 16 may include three or more electrodes, where each electrode may deliver therapy and/or detect intrinsic signals. ATP delivered by IPD 16, as compared with alternative devices, may be considered to be “painless” to patient 14 or even undetectable by patient 14 since the electrical stimulation occurs very close to or at cardiac muscle and at relatively low energy levels.

Fixation mechanisms 62 may attach IPD 16 to cardiac tissue. Fixation mechanisms 62 may be active fixation tines, screws, clamps, adhesive members, or any other types of attaching a device to tissue. As shown in the example of FIG. 2, fixation mechanisms 62 may be constructed of a memory material that retains a preformed shape. During implantation, fixation mechanisms 62 may be flexed forward to pierce tissue and allowed to flex back towards case 50. In this manner, fixation mechanisms 62 may be embedded within the target tissue.

Flange 54 may be provided on one end of case 50 to enable tethering or extraction of IPD 16. For example, a suture or other device may be inserted around flange 54 and/or through opening 56 and attached to tissue. In this manner, flange 54 may provide a secondary attachment structure to tether or retain IPD 16 within heart 18 if fixation mechanisms 62 fail. Flange 54 and/or opening 56 may also be used to extract IPD 16 once the IPD needs to be explanted (or removed) from patient 14 if such action is deemed necessary.

The techniques described herein may generally be described with regard to a leadless pacing device such as IPD 16. IPD 16 may be an example of an anti-tachycardia pacing device (ATPD). However, alternative implantable medical devices may be used to perform the same or similar functions as IPD 16, e.g., delivering ATP to heart 26 and, in some examples, communicate with ICD 9. In some examples, ICD 9 may determine the local electrogram and/or the far-field electrogram and may communicate with IPD 16. In some examples, IPD 16 may include one or more relatively short leads configured to place one or more respective additional electrodes at another location within the same chamber of the heart or a different chamber of the heart. In this manner, the housing of the ATPD may not carry all of the electrodes used to deliver ATP or perform other functions. In other examples, each electrode of IPD 16 may be carried by one or more leads (e.g., the housing of IPD 16 may not carry any of the electrodes). In some examples, system 8 may exclude IPD 16 or IPD 16 may not be able to deliver pacing (e.g. due to expiration or power source or malfunction) and ICD 9 may instead deliver pacing to heart 26. In other examples, both IPD 16 and ICD 9 may deliver pacing.

In another example, the ATPD may be configured to be implanted external to heart 26, e.g., near or attached to the epicardium of heart 26. An electrode carried by the housing of the ATPD may be placed in contact with the epicardium and/or one or more electrodes of leads coupled to the ATPD may be placed in contact with the epicardium at locations sufficient to provide therapy such as ATP (e.g., on external surfaces of the left and/or right ventricles). In any example, subcutaneous ICD 9 may communicate with one or more leadless or leaded devices implanted internal or external to heart 26.

FIG. 3 is a schematic diagram of another example implantable medical device system 100 in conjunction with a patient 114. As illustrated in FIG. 3, a medical device system 100 for sensing cardiac events (e.g., P-waves, R-waves, QRS complexes, etc.) and detecting tachyarrhythmia episodes may include PCD 110, right ventricular lead 118, left ventricular lead 120, atrial lead 121, and insertable cardiac monitor (ICM) 300. In one example, PCD 110 may be embodied as an implantable cardioverter-defibrillator (ICD) capable of delivering pacing, cardioversion and defibrillation therapy to the heart 116 of a patient 114. Right ventricular lead 118, left ventricular lead 120 and atrial lead 121 are electrically coupled to PCD 110 and extend into the patient's heart 116 via a vein. Right ventricular lead 118 includes electrodes 122 and 124 shown positioned on the lead in the patient's right ventricle (RV) for sensing ventricular electrogram signals and pacing in the RV. Left ventricular lead 120 includes electrode 130 positioned in the patient's left ventricle. Atrial lead 121 includes electrodes 126 and 128 positioned on the lead in the patient's right atrium (RA) for sensing atrial electrogram signals and pacing in the RA.

Right ventricular lead 118 additionally carries high voltage coil electrodes 142 and 144 used to deliver cardioversion and defibrillation shock pulses. Each of left ventricle lead 118, right ventricular lead 120 and the atrial lead 121 may be used to acquire intracardiac electrogram signals from the patient 114 and/or to deliver therapy in response to the acquired data. PCD 110 is shown as a dual chamber ICD, but in some examples, system 100 may be embodied as a multi-chamber system including a coronary sinus lead extending into the right atrium, through the coronary sinus and into a cardiac vein to position electrodes (e.g., electrode 130) along the left ventricle (LV) for sensing LV electrogram signals and delivering pacing pulses to the LV.

Implantable medical device circuitry configured for performing the functions of PCD 110 described herein and associated battery or batteries are housed within a sealed housing 112. Housing 112 may be conductive so as to serve as an electrode for use as an indifferent electrode during pacing or sensing or as an active electrode during defibrillation. As such, housing 112 is also referred to herein as “housing electrode” 112.

ICM 300 may be a device for sensing extracardiac ECG signals. ICM 300 may be implanted within patient 14 and may communicate with PCD 110 and/or external device 21. ICM 300 may include a plurality of electrodes for sensing ECG signals. In some examples, ICM 300 may determine the far-field electrogram, while PCD 110 may determine the near-field electrogram according to the techniques of this disclosure. ICM 300 will be described in further detail below with reference to FIG. 4.

EGM signal data acquired by PCD 110 may be transmitted to an external device 21. External device 21 may be embodied as a programmer, e.g. used in a clinic or hospital to communicate with PCD 110 via wireless telemetry. External device 21 may be coupled to a remote patient monitoring system, such as Carelink™, available from Medtronic plc, of Dublin, Ireland. External device 21 is used to program commands or operating parameters into PCD 110 for controlling IMD function and to interrogate PCD 110 to retrieve data, including device operational data as well as physiological data accumulated in IMD memory. Examples of communication techniques used by PCD 110 and external device 21 include low frequency or radiofrequency (RF) telemetry, which may be an RF link established via Bluetooth, WiFi, or MICS.

External device 21 may be configured to communicate with one or both of PCD 110 and ICM 300. In examples where external device 21 only communicates with one of PCD 110 and ICM 300, the non-communicative device may receive instructions from or transmit data to the device in communication with external device 21. In some examples, external device 21 comprises a handheld computing device, computer workstation, or networked computing device. External device 21 may include a user interface that receives input from a user. In other examples, the user may also interact with external device 21 remotely via a networked computing device. The user may interact with external device 21 to communicate with PCD 110 and/or ICM 300. For example, the user may interact with external device 21 to send an interrogation request and retrieve therapy delivery data, update therapy parameters that define therapy, manage communication between PCD 110 and/or ICM 300, or perform any other activities with respect to PCD 110 and/or ICM 300. Although the user is a physician, technician, surgeon, electrophysiologist, or other healthcare professional, the user may be patient 14 in some examples.

External device 21 may also allow the user to define how PCD 110 and/or ICM 300 senses electrical signals (e.g., ECGs), detects arrhythmias such as tachyarrhythmias, delivers therapy, and communicates with other devices of system 100. For example, external device 21 may be used to change tachyarrhythmia detection parameters. In another example, external device 21 may be used to manage therapy parameters that define therapies such as ATP therapy. Moreover, external device 21 may be used to alter communication protocols between PCD 110 and ICM 300.

External device 21 may communicate with PCD 110 and/or ICM 300 via wireless communication using any techniques known in the art. Examples of communication techniques are described above with reference to FIG. 1A. In some examples, external device 21 may include a programming head that may be placed proximate to patient 14's body near the PCD 110 and/or ICM 300 implant site in order to improve the quality or security of communication between PCD 110 and/or ICM 300 and external device 21.

In some examples, PCD 110 and ICM 300 may engage in communication to facilitate the appropriate detection of arrhythmias and/or delivery of anti-tachyarrhythmia therapy. Anti-arrhythmia therapy may include ATP. The communication may include one-way communication in which one device is configured to transmit communication messages and the other device is configured to receive those messages. The communication may instead include two-way communication in which each device is configured to transmit and receive communication messages. Although the examples below describe detection of tachyarrhythmias and the delivery of ATP, PCD 110 and ICM 300 may be configured to communicate with each other and provide alternative electrical stimulation therapies.

In some examples, system 100 may exclude ICM 300 and PCD 110 may deliver ATP therapy, sense evoked responses, and/or modify the ATP therapy based on the sensed evoked responses independently and/or in coordination with external device 21. In such an example, PCD 100 may use a plurality of pacing vectors to deliver ATP therapy to different locations in the heart without the need of ICM 300.

FIG. 4 is a conceptual drawing illustrating an example configuration of the insertable cardiac monitor (ICM) 300 of implantable medical device system 100 of FIG. 3. In the example shown in FIG. 4, ICM 300 may be embodied as a monitoring device having housing 302, proximal electrode 304 and distal electrode 306. Housing 302 may further comprise first major surface 308, second major surface 310, proximal end 312, and distal end 314. Housing 302 encloses electronic circuitry and a power source (shown in FIG. 9) located inside the ICM 300 and protects the circuitry contained therein from body fluids. Electrical feedthroughs provide electrical connection of electrodes 304 and 306.

In the example shown in FIG. 4, ICM 300 is defined by a length L, a width W and thickness or depth D and is in the form of an elongated rectangular prism wherein the length L is much larger than the width W, which in turn is larger than the depth D. In one example, the geometry of the ICM 300—in particular a width W greater than the depth D—is selected to allow ICM 300 to be inserted under the skin of the patient using a minimally invasive procedure and to remain in the desired orientation during insertion. For example, the device shown in FIG. 4 includes radial asymmetries (notably, the rectangular shape) along the longitudinal axis that maintains the device in the proper orientation following insertion. For example, in one example the spacing between proximal electrode 304 and distal electrode 306 may range from 30 millimeters (mm) to 55 mm, 35 mm to 55 mm, and from 40 mm to 55 mm and may be any range or individual spacing from 25 mm to 60 mm. In addition, ICM 300 may have a length L that ranges from 30 mm to about 70 mm. In other examples, the length L may range from 40 mm to 60 mm, 45 mm to 60 mm and may be any length or range of lengths between about 30 mm and about 70 mm. In addition, the width W of major surface 308 may range from 3 mm to 10 mm and may be any single or range of widths between 3 mm and 10 mm. The thickness of depth D of ICM 300 may range from 2 mm to 9 mm. In other examples, the depth D of ICM 300 may range from 2 mm to 5 mm and may be any single or range of depths from 2 mm to 9 mm. In addition, ICM 300 according to an example of the present disclosure is has a geometry and size designed for ease of implant and patient comfort. Examples of ICM 300 described in this disclosure may have a volume of three cubic centimeters (cm) or less, 1.5 cubic cm or less or any volume between three and 1.5 cubic centimeters.

In the example shown in FIG. 4, once inserted within the patient, the first major surface 308 faces outward, toward the skin of the patient while the second major surface 310 is located opposite the first major surface 308. In addition, in the example shown in FIG. 4, proximal end 312 and distal end 314 are rounded to reduce discomfort and irritation to surrounding tissue once inserted under the skin of the patient.

Proximal electrode 304 and distal electrode 306 are used to sense cardiac signals, e.g. ECG signals, intra-thoracically or extra-thoracically, which may be sub-muscularly or subcutaneously. ECG signals may be stored in a memory of the ICM 300, and ECG data may be transmitted via integrated antenna 322 to another medical device, which may be another implantable device or an external device, such as PCD 110 or external device 21. In some example, electrodes 304 and 306 may additionally or alternatively be used for sensing any bio-potential signal of interest, which may be, for example, an electrogram, EEG, EMG, or a nerve signal, from any implanted location.

In the example shown in FIG. 4, proximal electrode 304 is in close proximity to the proximal end 312 and distal electrode 306 is in close proximity to distal end 314. In this example, distal electrode 306 is not limited to a flattened, outward facing surface, but may extend from first major surface 308 around rounded edges 316 and/or end surface 318 and onto the second major surface 310 so that the electrode 306 has a three-dimensional curved configuration. In the example shown in FIG. 4, proximal electrode 304 is located on first major surface 308 and is substantially flat, outward facing. However, in other examples proximal electrode 304 may utilize the three-dimensional curved configuration of distal electrode 306, providing a three dimensional proximal electrode (not shown in this example). Similarly, in other examples distal electrode 306 may utilize a substantially flat, outward facing electrode located on first major surface 308 similar to that shown with respect to proximal electrode 304. The various electrode configurations allow for configurations in which proximal electrode 304 and distal electrode 306 are located on both first major surface 308 and second major surface 310. In other configurations, such as that shown in FIG. 4, only one of proximal electrode 304 and distal electrode 306 is located on both major surfaces 308 and 310, and in still other configurations both proximal electrode 304 and distal electrode 306 are located on one of the first major surface 308 or the second major surface 310 (i.e., proximal electrode 304 located on first major surface 308 while distal electrode 306 is located on second major surface 310). In another example, ICM 300 may include electrodes on both major surface 308 and 310 at or near the proximal and distal ends of the device, such that a total of four electrodes are included on ICM 300. Electrodes 304 and 306 may be formed of a plurality of different types of biocompatible conductive material, e.g. stainless steel, titanium, platinum, iridium, or alloys thereof, and may utilize one or more coatings such as titanium nitride or fractal titanium nitride.

In the example shown in FIG. 4, proximal end 312 includes a header assembly 320 that includes one or more of proximal electrode 304, integrated antenna 322, anti-migration projections 324, and/or suture hole 326. Integrated antenna 322 is located on the same major surface (i.e., first major surface 308) as proximal electrode 304 and is also included as part of header assembly 320. Integrated antenna 322 allows ICM 300 to transmit and/or receive data. In other examples, integrated antenna 322 may be formed on the opposite major surface as proximal electrode 304, or may be incorporated within the housing 322 of ICM 300. In the example shown in FIG. 4, anti-migration projections 324 are located adjacent to integrated antenna 322 and protrude away from first major surface 308 to prevent longitudinal movement of the device. In the example shown in FIG. 4, anti-migration projections 324 includes a plurality (e.g., nine) small bumps or protrusions extending away from first major surface 308. As discussed above, in other examples anti-migration projections 324 may be located on the opposite major surface as proximal electrode 304 and/or integrated antenna 322. In addition, in the example shown in FIG. 4 header assembly 320 includes suture hole 326, which provides another means of securing ICM 300 to the patient to prevent movement following insert. In the example shown, suture hole 326 is located adjacent to proximal electrode 304. In one example, header assembly 320 is a molded header assembly made from a polymeric or plastic material, which may be integrated or separable from the main portion of ICM 300.

According to the techniques of this disclosure, any combination of IPD 16, ICD 9, and PCD 110, may be a medical device system that may determine a first feature, such as a fiducial point in a local electrogram. For example, the medical device system may determine a first feature in an electrogram between a tip electrode and a ring electrode. The medical device system may determine a second feature, such as a QRS onset, in a far-field electrogram. For example, the medical device system may determine a second feature between a coil electrode and a can electrode. The medical device system may determine a first propagation time based on the first feature and the second feature. The medical device system may determine, based on the first propagation time, a number of pulses of an ATP train to achieve a second propagation time. The medical device system may deliver the ATP train of at least the number of pulses. While the techniques of this disclosure are sometimes discussed herein as being performed by any of IPD 16, ICD 9, and PCD 110, in some examples, as mentioned above, the techniques of this disclosure may be performed by any combination of IPD 16, ICD 9, or PCD 110. In some examples, the techniques of this disclosure may be performed by any combination of IPD 16, ICD 9, PCD 110, external device 21, or ICM 300.

According to the techniques of this disclosure, any of IPD 16, ICD 9, and PCD 110, may be a part of (or in some cases, all of) a medical device system that may determine a first feature, such as a fiducial point, in a local electrogram. The medical device system may control an electrode to pace a heart of a patient. The medical device system may determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective second feature, such as a QRS onset, in a respective electrogram. The device may determine, for each electrode of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the second feature. The medical device system may compare the respective propagation times associated with each of the plurality of other electrodes. The medical device system may determine, based on the comparison, an electrode associated with a shortest respective propagation time. The medical device system may select the electrode associated with the shortest respective propagation time for delivery of the ATP therapy. The medical device system may deliver the ATP therapy via the selected electrode.

Example configurations of these devices, including how they function to perform these tasks, are discussed in further detail below.

FIG. 5 is a functional block diagram illustrating an example configuration of IPD 16 of FIGS. 1A-1C and 2. In the illustrated example, IPD 16 includes processing circuitry 264, memory 226, therapy delivery circuitry 270, sensing circuitry 272, communication circuitry 268, and power source 274. The electronic components may receive power from a power source 274, which may be a rechargeable or non-rechargeable battery. In other examples, IPD 16 may include more or fewer electronic components. The described circuitry may be implemented together on a common hardware component or separately as discrete but interoperable hardware or software components. Depiction of different features as circuitry is intended to highlight different functional aspects and does not necessarily imply that such circuitry must be realized by separate hardware or software components. Rather, functionality associated with one or more circuitry may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

Memory 226 includes computer-readable instructions that, when executed by processing circuitry 264, cause IPD 16 and processing circuitry 264 to perform various functions attributed to IPD 16 and processing circuitry 264 herein (e.g., delivering anti-tachycardia pacing, sensing an evoked response, and/or modifying the ATP therapy). Memory 226 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processing circuitry 264 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 264 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 264 herein may be embodied as software, firmware, hardware or any combination thereof.

Therapy delivery circuitry 270 is electrically coupled to electrodes 52 and 60 carried on the housing of IPD 16. Therapy delivery circuitry 270 may include one or more pulse generators, capacitors, and/or other components capable of generating and/or storing energy to deliver as pacing therapy. In the illustrated example, therapy delivery circuitry 270 is configured to generate and deliver electrical stimulation therapy to heart 26. For example, therapy delivery circuitry 270 may deliver the electrical stimulation therapy to a portion of cardiac muscle within heart 26 via electrodes 52 and 60. In some examples, therapy delivery circuitry 270 may deliver pacing stimulation, e.g., ATP therapy, in the form of voltage or current electrical pulses. In other examples, therapy delivery circuitry 270 may deliver stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

Processing circuitry 264 controls therapy delivery circuitry 270 to deliver cardiac pacing therapy to heart 26 according to parameters, which may be stored in memory 226. For example, processing circuitry 264 may control therapy delivery circuitry 270 to deliver pacing pulses with the amplitudes, pulse widths, frequency, or electrode polarities specified by the therapy parameters, including intervals that define under what conditions and when pacing pulses should be delivered. In this manner, therapy delivery circuitry 270 may deliver pacing pulses (e.g., ATP pulses) to heart 26 via electrodes 52 and 60. Although IPD 16 may only include two electrodes, e.g., electrodes 52 and 60, IPD 16 may utilize three or more electrodes in other examples. IPD 16 may use any combination of electrodes to deliver therapy and/or detect electrical signals from patient 14.

Processing circuitry 264 may control therapy delivery circuitry 270 to deliver pacing pulses for ATP therapy according to ATP parameters 276 stored in memory 266. ATP therapy parameters 276 may include pulse intervals, pulse width, current and/or voltage amplitudes, and durations for each pacing mode. In some examples, ATP parameters 276 may include a plurality of ranges of propagation times and associated numbers of pulses of an ATP train, a formula that may be applied to a first propagation time, a linear equation that may be applied to a first propagation time, a continuous function that may be applied to a first propagation time, or a look-up table that may include first propagation times and associated number of pulses of an ATP train. For example, the pulse interval may be based on a fraction of the detected ventricular tachycardia (VT) cycle length and be between approximately 150 milliseconds and 500 milliseconds (e.g., between approximately 2.0 hertz and 7.0 hertz), and the pulse width may be between approximately 0.5 milliseconds and 2.0 milliseconds. The amplitude of each pacing pulse may be between approximately 2.0 volts and 10.0 volts. In some examples, the pulse amplitude may be approximately 6.0 V and the pulse width may be approximately 1.5 milliseconds; another example may include pulse amplitudes of approximately 5.0 V and pulse widths of approximately 1.0 milliseconds.

Each train of pulses during ATP may last for a duration of between approximately 70 milliseconds to approximately 15 seconds or be defined as a specific number of pulses. According to the techniques of this disclosure, processing circuitry 264 of IPD 16 may determine the length or duration of an ATP train, such as the first ATP train during a VT event. For example, processing circuitry 264 may determine a first feature, such as a fiducial point, in a local electrogram. Processing circuitry 264 may determine a second feature, such as a QRS onset, in a far-field electrogram. Processing circuitry 264 may determine a propagation time based on the first feature and the second feature. Processing circuitry 264 may determine a number of pulses of the ATP train to achieve a second propagation time based on the first propagation time. Processing circuitry 264 may control therapy delivery circuitry 270 to deliver the ATP train of at least the number of pulses.

Each pulse, or burst of pulses, may include a ramp up in amplitude or in pulse rate. In addition, trains of pulses in successive ATP periods may be delivered at increasing pulse rate in an attempt to capture the heart and terminate the tachycardia. Example ATP parameters and other criteria involving the delivery of ATP are described in U.S. Pat. No. 6,892,094 to Ousdigian et al., entitled, “COMBINED ANTI-TACHYCARDIA PACING (ATP) AND HIGH VOLTAGE THERAPY FOR TREATING VENTRICULAR ARRHYTHMIAS,” and issued on May 10, 2005, the entire content of which is incorporated herein by reference and U.S. Pat. No. 8,706,221 to Belk et al., entitled, “METHOD AND DEVICE FOR DELIVERYING ANTI-TACHYCARDIA PACING THERAPY,” and issued on Apr. 22, 2014, the entire content of which is incorporated herein by reference.

Processing circuitry 264 controls therapy delivery circuitry 270 to generate and deliver pacing pulses with any of a number of shapes, amplitudes, pulse widths, or other characteristic to capture the heart. For example, the pacing pulses may be monophasic, biphasic, or multi-phasic (e.g., more than two phases). The pacing thresholds of the heart when delivering pacing pulses may depend upon a number of factors, including location, type, size, orientation, and/or spacing of IPD 16 and/or electrodes 52 and/or 60, physical abnormalities of the heart (e.g., pericardial adhesions or myocardial infarctions), or other factor(s).

In examples in which IPD 16 includes more than two electrodes, therapy delivery circuitry 270 may include a switch and processing circuitry 264 may use the switch to select, e.g., via a data/address bus, which of the available electrodes are used to deliver pacing pulses. The switch may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

Sensing circuitry 272 is electrically connected to and monitors signals from some or all of electrodes 52 and 60 in order to monitor electrical activity of heart 26, impedance, or other electrical phenomenon. Sensing may be done to determine heart rates or heart rate variability, or to detect arrhythmias (e.g., tachyarrhythmias or bradycardia) or other electrical signals. Sensing circuitry 272 may also include a switch to select which of the available electrodes (or electrode polarity) are used to sense the heart activity, depending upon which electrode combination, or electrode vector, is used in the current sensing configuration. In examples with several electrodes, processing circuitry 264 may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch circuitry within sensing circuitry 272. Sensing circuitry 272 may include one or more detection channels, each of which may be coupled to a selected electrode configuration for detection of cardiac signals via that electrode configuration. Some detection channels may be configured to detect cardiac events, such as fiducial points, QRS complexes, P- or R-waves, and provide indications of the occurrences of such events to processing circuitry 264, e.g., as described in U.S. Pat. No. 5,117,824 to Keimel et al., which issued on Jun. 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Processing circuitry 264 may control the functionality of sensing circuitry 272 by providing signals via a data/address bus.

According to the techniques of this disclosure, processing circuitry 264 may control therapy delivery circuitry 270 to deliver via an electrode pacing to the heart of a patient. Processing circuitry 264 may determine a first feature, such as a fiducial point, in a local electrogram in response to the pace. For example, sensing circuitry 272 may sense a signal between a tip electrode and a ring electrode and processing circuitry 264 may determine the first feature in the sensed signal. Processing circuitry 264 may also determine, for each electrode of a plurality of other electrodes communicatively coupled to a medical device system, a respective second feature, such as a QRS onset, in a respective electrogram. For example, sensing circuitry 272 may sense a signal between electrodes and processing circuitry 264 may determine a respective QRS onset. Processing circuitry 264 may determine, for each electrode of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and a respective second feature. Processing circuitry 264 may compare the respective propagation times associated with each of the plurality of other electrodes. Processing circuitry 264 may determine, based on the comparison, an electrode associated with a shortest propagation time. Processing circuitry 264 may select the electrode associated with the shortest propagation time for delivery of the ATP therapy. Processing circuitry 264 may control therapy delivery circuitry 270 to deliver the ATP therapy via the selected electrode. For example, processing circuitry 264 may use a switch to select the electrode to deliver the ATP therapy.

The components of sensing circuitry 272 may be analog components, digital components or a combination thereof. Sensing circuitry 272 may, for example, include one or more sense amplifiers, filters, rectifiers, threshold detectors, analog-to-digital converters (ADCs) or the like. Sensing circuitry 272 may convert the sensed signals to digital form and provide the digital signals to processing circuitry 264 for processing or analysis. For example, sensing circuitry 272 may amplify signals from the sensing electrodes and convert the amplified signals to multi-bit digital signals by an ADC. Sensing circuitry 272 may also compare processed signals to a threshold to detect the existence of atrial or ventricular depolarizations (e.g., P- or R-waves) and indicate the existence of the atrial depolarization (e.g., P-waves) or ventricular depolarizations (e.g., R-waves) to processing circuitry 264.

Sensing circuitry 272 and/or processing circuitry 264 may also include circuitry for measuring the capture threshold for the delivery of pacing pulses via electrodes 52 and 60. The capture threshold may indicate the voltage and pulse width necessary to induce depolarization of the surrounding cardiac muscle. For example, processing circuitry 264 may periodically control therapy delivery circuitry 270 to modify the amplitude of pacing pulses delivered to patient 12, and sensing circuitry 272 and/or processing circuitry 264 may detect whether the surrounding cardiac tissue depolarized in response to the pacing pulses, i.e., detected whether there was an evoked response to the pacing pulse. Processing circuitry 264 may determine the capture threshold based on the amplitude where loss of capture occurred.

Processing circuitry 264 may process the signals from sensing circuitry 272 to monitor electrical activity of the heart of the patient. Processing circuitry 264 may store signals obtained by sensing circuitry 2272 as well as any generated electrogram waveforms, marker channel data or other data derived based on the sensed signals in memory 266. Processing circuitry 264 may analyze the electrogram waveforms and/or marker channel data to detect cardiac events (e.g., tachycardia). In response to detecting the cardiac event, processing circuitry 264 may control therapy delivery circuitry 270 to deliver the desired therapy to treat the cardiac event, e.g., ATP therapy.

In examples in which IPD 16 includes more than two electrodes, therapy delivery circuitry 270 may include a switch and processing circuitry 264 may use the switch to select, e.g., via a data/address bus, which of the available electrodes are used to deliver pacing pulses. The switch may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes. Processing circuitry 264 may select the electrodes to function as signal electrodes, or the signal vector, via the switch circuitry within therapy delivery circuitry 270. In some instances, the same switch circuitry may be used by both therapy delivery circuitry 270 and sensing circuitry 272. In other instances, each of sensing circuitry 272 and therapy delivery circuitry 270 may have separate switch circuitry.

Processing circuitry 264 may include a timing and control circuitry, which may be embodied as hardware, firmware, software, or any combination thereof. The timing and control circuitry may comprise a dedicated hardware circuit, such as an ASIC, separate from other processing circuitry 264 components, such as a microprocessor, or a software module executed by a component of processing circuitry 264, which may be a microprocessor or ASIC. The timing and control circuitry may implement programmable counters. If IPD 16 is configured to generate and deliver pacing pulses to heart 26, such counters may control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of pacing.

Intervals defined by the timing and control circuitry within processing circuitry 264 may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and the pulse widths of the pacing pulses. As another example, the timing and control circuitry may withhold sensing from one or more channels of sensing circuitry 272 for a time interval during and after delivery of electrical stimulation to heart 26. The durations of these intervals may be determined by processing circuitry 264 in response to stored data in memory 226. The timing and control circuitry of processing circuitry 264 may also determine the amplitude of the cardiac pacing pulses.

Interval counters implemented by the timing and control circuitry of processing circuitry 264 may be reset upon sensing of R-waves and P-waves with detection channels of sensing circuitry 272. In examples in which IPD 16 provides pacing, therapy delivery circuitry 270 may include pacer output circuits that are coupled to electrodes 52 and 60, for example, appropriate for delivery of a bipolar or unipolar pacing pulse to one of the chambers of heart 26. In such examples, processing circuitry 264 may reset the interval counters upon the generation of pacing pulses by therapy delivery circuitry 270, and thereby control the basic timing of cardiac pacing functions, including ATP or post-shock pacing.

The value of the count present in the interval counters when reset by sensed R-waves and P-waves may be used by processing circuitry 264 to measure the durations of R-R intervals, P-P intervals, P-R intervals and R-P intervals, which are measurements that may be stored in memory 266. Processing circuitry 264 may use the count in the interval counters to detect a tachyarrhythmia event, such as atrial fibrillation (AF), atrial tachycardia (AT), VF, or VT. These intervals may also be used to detect the overall heart rate, ventricular contraction rate, and heart rate variability. A portion of memory 266 may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by processing circuitry 264 in response to the occurrence of a pace or sense interrupt to determine whether the patient's heart 26 is presently exhibiting atrial or ventricular tachyarrhythmia.

In some examples, an arrhythmia detection method may include any suitable tachyarrhythmia detection algorithms.

In some examples, processing circuitry 264 may determine that tachyarrhythmia has occurred by identification of shortened R-R (or P-P) interval lengths. Generally, processing circuitry 264 detects tachycardia when the interval length falls below 220 milliseconds and fibrillation when the interval length falls below 180 milliseconds. In other examples, processing circuitry 264 may detect ventricular tachycardia when the interval length falls between 330 milliseconds and ventricular fibrillation when the interval length falls below 240 milliseconds. These interval lengths are merely examples, and a user may define the interval lengths as desired, which may then be stored within memory 266. This interval length may need to be detected for a certain number of consecutive cycles, for a certain percentage of cycles within a running window, or a running average for a certain number of cardiac cycles, as examples. In other examples, additional physiological parameters may be used to detect an arrhythmia. For example, processing circuitry 264 may analyze one or more morphology measurements, impedances, or any other physiological measurements to determine that patient 14 is experiencing a tachyarrhythmia.

In the event that an ATP regimen is desired, timing intervals for controlling the generation of ATP therapies by therapy deliver circuitry 270 may be loaded by processing circuitry 264 into the timing and control circuitry based on ATP parameters 276 to control the operation of the escape interval counters therein and to define refractory periods during which detection of R-waves and P-waves is ineffective to restart the escape interval counters for the ATP. An ATP regimen may be desired if processing circuitry 264 detects an atrial or ventricular tachyarrhythmia based on signals from sensing circuitry 272, and/or receives a command from another device or system, such as ICD 9, as examples.

In addition to detecting and identifying specific types of cardiac rhythms, sensing circuitry 272 may also sample the detected intrinsic signals to generate an electrogram or other time-based indication of cardiac events. Processing circuitry 264 may also be able to coordinate the delivery of pacing pulses from different IPDs implanted in different chambers of heart 26, such as an IPD implanted in atrium and/or an IPD implanted in left ventricle. For example, processing circuitry 264 may identify delivered pulses from other IPDs via sensing circuitry 272 and update pulse timing to accomplish a selected pacing regimen. This detection may be on a pulse-to-pulse or beat-to-beat basis, or on a less frequent basis to make slight modifications to pulse rate over time. In other examples, IPDs may communicate with each other via communication circuitry 268 and/or instructions over a carrier wave (such as a stimulation waveform). In this manner, ATP pacing may be coordinated from multiple IPDs.

IPD 16 may deliver ATP therapy using electrodes 52 and 60 and therapy delivery circuitry 270 and may sense a local evoked response using the electrodes 52 and 60 and sensing circuitry 272 to sense at a location that is at or near the location of the delivery of the ATP therapy. Another device, such as ICD 9 may sense a global evoked response to the ATP pacing delivered by IPD 16 by sensing at a location that is a substantial distance from the location of the delivery of the ATP therapy. In other examples, the same device, using different electrode vectors, may be used to sense both local and global evoked responses to delivered ATP therapy delivered by the device. The evoked responses may be detected via the hardware of sensing circuitry 272 similar to R-wave, e.g., using a sense amplifier to detect amplitude above a threshold shortly after delivery of a pacing pulse, and/or may be by detected by processing circuitry 264 determining a spike by signal processing a digitized version of ECG signals from electrodes 52 and 60.

Memory 266 may be configured to store a variety of operational parameters, therapy parameters, including ATP therapy parameters 276, sensed and detected data, and any other information related to the therapy and treatment of patient 14. In the example of FIG. 5, memory 266 may store sensed ECGs, detected arrhythmias, communications from ICD 9, and therapy parameters that define ATP therapy (ATP therapy parameters 276). In other examples, memory 266 may act as a temporary buffer for storing data until it can be uploaded to ICD 9, another implanted device, or external device 21.

Communication circuitry 268 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 21 (FIGS. 1A-1C and 7), ICD 9 (FIGS. 1A-1C and 6), a clinician programmer, a patient monitoring device, or the like. For example, communication circuitry 284 may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifier components for transmission and reception of data. Under the control of processing circuitry 264, communication circuitry 268 may receive downlink telemetry from and send uplink telemetry to external device 21 with the aid of an antenna, which may be internal and/or external. Processing circuitry 264 may provide the data to be uplinked to external device 21 and the control signals for the telemetry circuit within communication circuitry 268, e.g., via an address/data bus. In some examples, communication circuitry 268 may provide received data to processing circuitry 264 via a multiplexer.

In some examples, IPD 16 may signal external device 21 to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic plc., of Dublin, Ireland, or some other network linking patient 14 to a clinician. IPD 16 may spontaneously transmit information to the network or in response to an interrogation request from a user.

Power source 274 may be any type of device that is configured to hold a charge to operate the circuitry of IPD 16. Power source 274 may be provided as a rechargeable or non-rechargeable battery. In other example, power source 274 may incorporate an energy scavenging system that stores electrical energy from movement of IPD 16 within patient 14.

The various circuitry of IPD 16 may include any one or more processors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or equivalent discrete or integrated circuitry, including analog circuitry, digital circuitry, or logic circuitry.

According to the techniques of this disclosure, IPD 16 may determine a first feature, such as a fiducial point, in a local electrogram, determine a second feature, such as a QRS onset, in a far-field electrogram, determine a first propagation time based on the first feature and the second feature, determine, based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time, and deliver the ATP train of at least the number of pulses.

According to the techniques of this disclosure, IPD 16 may control an electrode to pace a heart of a patient, determine a first feature in a local electrogram, determine, for each electrode of a plurality of other electrodes communicatively coupled to a medical device system (which may include IPD 16), a respective propagation time based on the first feature and a respective second feature, in a respective electrogram, compare the respective propagation times associated with each of the plurality of other electrodes, determine, based on the comparison, an electrode associated with a shortest relative propagation time, and select the electrode associated with the shortest relative propagation time for delivery of the ATP therapy. A therapy delivery circuitry may deliver the ATP therapy via the selected electrode.

FIG. 6 is a functional block diagram illustrating an example configuration of ICD 9 of the implantable medical device system of FIGS. 1A-1C. In the illustrated example, ICD 9 includes processing circuitry 280, sensing circuitry 286, therapy delivery circuitry 288, communication circuitry 284, and memory 282. The electronic components may receive power from a power source 290, which may be a rechargeable or non-rechargeable battery. In other examples, ICD 9 may include more or fewer electronic components. The described circuitry may be implemented together on a common hardware component or separately as discrete but interoperable hardware or software components. Depiction of different features as circuitry is intended to highlight different functional aspects and does not necessarily imply that such circuitry must be realized by separate hardware or software components. Rather, functionality associated with one or more circuitry may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. FIG. 6 will be described in the context of ICD 9 being coupled to lead 10 for exemplary purposes only. However, ICD 9 may be coupled to other leads, and thus other electrodes.

Memory 282 includes computer-readable instructions that, when executed by processing circuitry 282, cause ICD 9 and processing circuitry 280 to perform various functions attributed to ICD 9 and processing circuitry 280 herein (e.g., delivering anti-tachycardia pacing, sensing an evoked response, and/or modifying the ATP therapy). Memory 282 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Sensing circuitry 286 is electrically coupled to some or all of electrode 28 (or separately to segments 28 a and/or 28 b) and 32 a and 32 b via the conductors of lead 10 (shown in FIGS. 1A-1C) and one or more electrical feedthroughs, or to the housing electrode via conductors internal to the housing of ICD 9. Sensing circuitry 286 is configured to obtain signals sensed via one or more combinations of electrode 28 (or separately to segments 28 a and/or 28 b), 32 a, 32 b and the housing electrode of ICD 9 and process the obtained signals.

The components of sensing circuitry 286 may be analog components, digital components or a combination thereof. Sensing circuitry 286 may, for example, include one or more sense amplifiers, filters, rectifiers, threshold detectors, analog-to-digital converters (ADCs) or the like. Sensing circuitry 286 may convert the sensed signals to digital form and provide the digital signals to processing circuitry 280 for processing or analysis. For example, sensing circuitry 286 may amplify signals from the sensing electrodes and convert the amplified signals to multi-bit digital signals by an ADC. Sensing circuitry 286 may also compare processed signals to a threshold to detect the existence of fiducial points, QRS complexes, and atrial or ventricular depolarizations (e.g., P- or R-waves) and indicate the existence of the atrial depolarization (e.g., P-waves) or ventricular depolarizations (e.g., R-waves) to processing circuitry 280.

Processing circuitry 280 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 280 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 280 herein may be embodied as software, firmware, hardware or any combination thereof.

Processing circuitry 280 may process the signals from sensing circuitry 286 to monitor electrical activity of the heart of the patient. Processing circuitry 280 may store signals obtained by sensing circuitry 286 as well as any generated electrogram waveforms, marker channel data or other data derived based on the sensed signals in memory 282. Processing circuitry 280 may analyze the electrogram waveforms and/or marker channel data to detect cardiac events (e.g., tachycardia). In response to detecting the cardiac event, processing circuitry 280 may control therapy delivery circuitry 280 to deliver the desired therapy to treat the cardiac event, e.g., ATP therapy.

Therapy delivery circuitry 288 is configured to generate and deliver electrical stimulation therapy to the heart. Therapy delivery circuitry 288 may include one or more pulse generators, capacitors, and/or other components capable of generating and/or storing energy to deliver as pacing therapy, defibrillation therapy, cardioversion therapy, cardiac resynchronization therapy, other therapy or a combination of therapies. In some instances, therapy delivery circuitry 288 may include a first set of components configured to provide pacing therapy and a second set of components configured to provide defibrillation therapy. In other instances, therapy delivery circuitry 288 may utilize the same set of components to provide both pacing and defibrillation therapy. In still other instances, therapy delivery circuitry 288 may share some of the defibrillation and pacing therapy components while using other components solely for defibrillation or pacing. In some examples, therapy delivery circuitry 288 may deliver pacing stimulation, e.g., ATP therapy, in the form of voltage or current electrical pulses. In other examples, therapy delivery circuitry 288 may deliver stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

Processing circuitry 280 may control therapy delivery circuitry 288 to deliver the generated therapy to the heart via one or more combinations of electrode 28 (or separately to segments 28 a and/or 28 b), 32 a, and 32 b of lead 10 and the housing electrode of ICD 9 according to one or more therapy programs, which may be stored in memory 282. In instances in which processing circuitry 280 is coupled to a different lead, other electrodes may be utilized. Processing circuitry 280 controls therapy delivery circuitry 288 to generate electrical stimulation therapy with the amplitudes, pulse widths, timing, frequencies, electrode combinations or electrode configurations specified by stored therapy programs.

Processing circuitry 264 controls therapy delivery circuitry 288 to deliver cardiac pacing therapy to heart 26 according to parameters, which may be stored in memory 282. For example, processing circuitry 280 may control therapy delivery circuitry 288 to deliver pacing pulses with the amplitudes, pulse widths, frequency, or electrode polarities specified by the therapy parameters, including intervals that define under what conditions and when pacing pulses should be delivered.

Processing circuitry 280 may control therapy delivery circuitry 288 to deliver ATP therapy based on ATP parameters 276 stored in memory 282 and may modify the ATP therapy by modifying ATP parameters 276 in memory 282. ATP therapy parameters 276 may include pulse intervals, pulse width, current and/or voltage amplitudes, and durations for each pacing mode. In some examples, ATP parameters 276 may include a plurality of ranges of propagation times and associated numbers of pulses of an ATP train, a formula that may be applied to a first propagation time, a linear equation that may be applied to a first propagation time, a continuous function that may be applied to a first propagation time, or a look-up table that may include first propagation times and associated numbers of pulses of an ATP train. For example, the pulse interval may be based on a fraction of the detected ventricular tachycardia (VT) cycle length and be between approximately 150 milliseconds and 500 milliseconds (e.g., between approximately 2.0 hertz and 7.0 hertz), and the pulse width may be between approximately 0.5 milliseconds and 2.0 milliseconds. The amplitude of each pacing pulse may be between approximately 2.0 volts and 10.0 volts. In some examples, the pulse amplitude may be approximately 6.0 V and the pulse width may be approximately 1.5 milliseconds; another example may include pulse amplitudes of approximately 5.0 V and pulse widths of approximately 1.0 milliseconds.

Each train of pulses during ATP may last for a duration of between approximately 70 milliseconds to approximately 15 seconds or be defined as a specific number of pulses. According to the techniques of this disclosure, processing circuitry 280 of ICD 9 may determine the length or duration of an ATP train, such as the first ATP train during a VT event. For example, processing circuitry 280 may determine a first feature, such as a fiducial point, in a local electrogram. Processing circuitry 280 may determine a second feature, such as a QRS onset, in a far-field electrogram. Processing circuitry 280 may determine a first propagation time based on the first feature and the second feature. Processing circuitry 280 may determine a number of pulses of the ATP train to achieve a second propagation time based on the first propagation time. Processing circuitry 280 may control therapy delivery circuitry 288 to deliver the ATP train of at least the number of pulses.

Each pulse, or burst of pulses, may include a ramp up in amplitude or in pulse rate. In addition, trains of pulses in successive ATP periods may be delivered at increasing pulse rate in an attempt to capture the heart and terminate the tachycardia.

Therapy delivery circuitry 288 may include switch circuitry to select which of the available electrodes are used to deliver the therapy. The switch circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple electrodes to therapy delivery circuitry 288. Processing circuitry 280 may select the electrodes to function as signal electrodes, or the signal vector, via the switch circuitry within therapy delivery circuitry 28. In instances in which defibrillation segments 28 a and 28 b are each coupled to separate conductors, processing circuitry 280 may be configured to selectively couples therapy delivery circuitry 288 to either one of segments 28 a and 28 b individually or couple to both of the segments 28 a and 28 b concurrently. In some instances, the same switch circuitry may be used by both therapy delivery circuitry 288 and sensing circuitry 286. In other instances, each of sensing circuitry 286 and therapy delivery circuitry 288 may have separate switch circuitry.

According to the techniques of this disclosure, processing circuitry 280 may control an electrode to pace a heart of a patient. Processing circuitry may determine a first feature in a local electrogram in response to the pace. For example, sensing circuitry 286 may sense a signal between a tip electrode and a ring electrode and processing circuitry 280 may determine the fiducial point in the sensed signal. Processing circuitry 280 may also determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective second feature, such as a QRS onset, in a respective electrogram. For example, sensing circuitry 286 may sense a signal between electrodes and processing circuitry 280 may determine a respective second feature. Processing circuitry 280 may determine, for each electrode of the other plurality of electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and a respective second feature. Processing circuitry 280 may compare the respective propagation times associated with each electrode of the plurality of other electrodes. Processing circuitry 280 may determine, based on the comparison, an electrode associated with a shortest propagation time. Processing circuitry 280 may select the electrode associated with the shortest propagation time for delivery of the ATP therapy. Processing circuitry 280 may control therapy delivery circuitry 286 to deliver the ATP therapy via the selected electrode. For example, processing circuitry 280 may use a switch to select the sense electrode to deliver the ATP therapy.

In one example, therapy delivery circuitry 288 may deliver pacing via an electrode vector that includes one or both defibrillation electrode segments 28 a and 28 b. The electrode vector used for pacing may be segment 28 a as an anode (or cathode) and one of electrodes 28 b, 32 a, 32 b, or the housing of ICD 9 as the cathode (or anode) or segment 28 b as an anode (or cathode) and one of electrodes 28 b, 32 a, 32 b, or the housing of ICD 9 as the cathode (or anode). In some examples, electrode 52 and/or electrode 60 of IPD 16 may be used as an anode or cathode and ICD 9 may communicate with 16 via communication circuitry 284 and/or external device may communicate with ICD 9 and IPD 16 to coordinate the use of electrodes of both ICD 9 and IPD 16.

Processing circuitry 280 controls therapy delivery circuitry 288 to generate and deliver pacing pulses with any of a number of shapes, amplitudes, pulse widths, or other characteristic to capture the heart. For example, the pacing pulses may be monophasic, biphasic, or multi-phasic (e.g., more than two phases). The pacing thresholds of the heart when delivering pacing pulses from the substernal space, e.g., from electrodes 32 a, 32 b and/or electrode segments 28 a and/or 28 b substantially within anterior mediastinum 36, may depend upon a number of factors, including location, type, size, orientation, and/or spacing of electrodes 32 a and 32 b and/or electrode segments 28 a and 28 b, location of ICD 9 relative to electrodes 32 a and 32 b and/or electrode segments 28 a and 28 b, physical abnormalities of the heart (e.g., pericardial adhesions or myocardial infarctions), or other factor(s).

Processing circuitry 280 may include a timing and control circuitry, which may be embodied as hardware, firmware, software, or any combination thereof. The timing and control circuitry may comprise a dedicated hardware circuit, such as an ASIC, separate from other processing circuitry 280 components, such as a microprocessor, or a software module executed by a component of processing circuitry 280, which may be a microprocessor or ASIC. The timing and control circuitry may implement programmable counters. If ICD 9 is configured to generate and deliver pacing pulses to heart 26, such counters may control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of pacing.

Intervals defined by the timing and control circuitry within processing circuitry 280 may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and the pulse widths of the pacing pulses. As another example, the timing and control circuitry may withhold sensing from one or more channels of sensing circuitry 286 for a time interval during and after delivery of electrical stimulation to heart 26. The durations of these intervals may be determined by processing circuitry 264 in response to stored data in memory 282. The timing and control circuitry of processing circuitry 264 may also determine the amplitude of the cardiac pacing pulses.

Interval counters implemented by the timing and control circuitry of processing circuitry 280 may be reset upon sensing of R-waves and P-waves with detection channels of sensing circuitry 286. In examples in which ICD 9 provides pacing, therapy delivery circuitry 288 may include pacer output circuits that are coupled to electrodes, for example, appropriate for delivery of a bipolar or unipolar pacing pulse to one of the chambers of heart 26. In such examples, processing circuitry 280 may reset the interval counters upon the generation of pacing pulses by therapy delivery circuitry 288, and thereby control the basic timing of cardiac pacing functions, including ATP or post-shock pacing.

The value of the count present in the interval counters when reset by sensed R-waves and P-waves may be used by processing circuitry 280 to measure the durations of R-R intervals, P-P intervals, P-R intervals and R-P intervals, which are measurements that may be stored in memory 282. Processing circuitry 280 may use the count in the interval counters to detect a tachyarrhythmia event, such as atrial fibrillation (AF), atrial tachycardia (AT), VF, or VT. These intervals may also be used to detect the overall heart rate, ventricular contraction rate, and heart rate variability. A portion of memory 282 may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by processing circuitry 280 in response to the occurrence of a pace or sense interrupt to determine whether the patient's heart 26 is presently exhibiting atrial or ventricular tachyarrhythmia.

In some examples, an arrhythmia detection method may include any suitable tachyarrhythmia detection algorithms. In some examples, processing circuitry 280 may determine that tachyarrhythmia has occurred by identification of shortened R-R (or P-P) interval lengths. Generally, processing circuitry 280 detects tachycardia when the interval length falls below 220 milliseconds and fibrillation when the interval length falls below 180 milliseconds. In other examples, processing circuitry 280 may detect ventricular tachycardia when the interval length falls between 330 milliseconds and ventricular fibrillation when the interval length falls below 240 milliseconds. These interval lengths are merely examples, and a user may define the interval lengths as desired, which may then be stored within memory 282. This interval length may need to be detected for a certain number of consecutive cycles, for a certain percentage of cycles within a running window, or a running average for a certain number of cardiac cycles, as examples. In other examples, additional physiological parameters may be used to detect an arrhythmia. For example, processing circuitry 280 may analyze one or more morphology measurements, impedances, or any other physiological measurements to determine that patient 14 is experiencing a tachyarrhythmia.

In the event that an ATP regimen is desired, timing intervals for controlling the generation of ATP therapies by therapy deliver circuitry 288 may be loaded by processing circuitry 280 into the timing and control circuitry based on ATP parameters 276 to control the operation of the escape interval counters therein and to define refractory periods during which detection of R-waves and P-waves is ineffective to restart the escape interval counters for the ATP. An ATP regimen may be desired if processing circuitry 280 detects an atrial or ventricular tachyarrhythmia based on signals from sensing circuitry 286, and/or receives a command from another device or system, such as IPD 16, as examples.

Memory 282 may be configured to store a variety of operational parameters, therapy parameters, including ATP therapy parameters 276, sensed and detected data, and any other information related to the therapy and treatment of patient 14. In the example of FIG. 6, memory 282 may store sensed ECGs, detected arrhythmias, communications from IPD 16, and therapy parameters that define ATP therapy (ATP therapy parameters 276). In other examples, memory 282 may act as a temporary buffer for storing data until it can be uploaded to IPD 16, another implanted device, or external device 21.

Communication circuitry 284 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 21 (FIGS. 1A-1C and 7), IPD 16 (FIGS. 1A-1C and FIG. 2), a clinician programmer, a patient monitoring device, or the like. For example, communication circuitry 284 may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifier components for transmission and reception of data with the aid of antenna 292. Antenna 292 may be located within connector block of ICD 9 or within the housing of ICD 9. Under the control of processing circuitry 280, communication circuitry 284 may receive downlink telemetry from and send uplink telemetry to external device 21 with the aid of antenna 292, which may be internal and/or external. Processing circuitry 280 may provide the data to be uplinked to external device 21 and the control signals for the telemetry circuit within communication circuitry 284, e.g., via an address/data bus. In some examples, communication circuitry 284 may provide received data to processing circuitry 280 via a multiplexer.

In some examples, ICD 9 may signal external device 21 to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic plc, of Dublin, Ireland, or some other network linking patient 14 to a clinician. ICD 9 may spontaneously transmit information to the network or in response to an interrogation request from a user.

Power source 290 may be any type of device that is configured to hold a charge to operate the circuitry of ICD 9. Power source 290 may be provided as a rechargeable or non-rechargeable battery. In other example, power source 290 may incorporate an energy scavenging system that stores electrical energy from movement of ICD 9 within patient 14.

The various circuitry of ICD 9 may include any one or more processors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or equivalent discrete or integrated circuitry, including analog circuitry, digital circuitry, or logic circuitry.

According to the techniques of this disclosure, ICD 9 may determine a first feature, such as a fiducial point, in a local electrogram, determine a second feature, such as a QRS onset, in a far-field electrogram, determine a first propagation time based on the first feature and the second feature, determine, based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time, and deliver the ATP train of at least the number of pulses.

According to the techniques of this disclosure, ICD 9 may control an electrode to pace a heart of a patient, determine a first feature in a local electrogram, determine, for each electrode of a plurality of other electrodes communicatively coupled to a medical device system (which may include ICD 9), a respective propagation time based on the first feature and a respective second feature, in a respective electrogram, compare the respective propagation times associated with each electrode of the plurality of other electrodes, determine, based on the comparison, an electrode associated with a shortest respective propagation time; and select the electrode associated with the shortest respective propagation time for delivery of the ATP therapy. Therapy delivery circuitry of ICD 9 may deliver the ATP therapy via the selected electrode.

FIG. 7 is a functional block diagram illustrating an example configuration of external device 21 of FIGS. 1A-1C and FIG. 3. External device 21 may include processing circuitry 400, memory 402, communication circuitry 408, user interface 406, and power source 404. Processing circuitry 400 controls user interface 406 and communication circuitry 408, and stores and retrieves information and instructions to and from memory 402. External device 21 may be configured for use as a clinician programmer or a patient programmer. Processing circuitry 400 may comprise any combination of one or more processors including one or more microprocessors, DSPs, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, processing circuitry 400 may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to processing circuitry 400.

A user, such as a clinician or patient 14, may interact with external device 21 through user interface 406. User interface 406 may include a display, such as an LCD or LED display or other type of screen, to present information related the ATP therapy, including ATP therapy parameters 276 store in any of memory 266 or memory 282. In addition, user interface 406 may include an input mechanism to receive input from the user. The input mechanisms may include, for example, buttons, a keypad (e.g., an alphanumeric keypad), a peripheral pointing device or another input mechanism that allows the user to navigate though user interfaces presented by processing circuitry 400 of external device 21 and provide input.

If external device 21 includes buttons and a keypad, the buttons may be dedicated to performing a certain function, i.e., a power button, or the buttons and the keypad may be soft keys that change in function depending upon the section of the user interface currently viewed by the user. Alternatively, a screen of external device 21 may be a touch screen that allows the user to provide input directly to the user interface shown on the display. The user may use a stylus or a finger to provide input to the display. In other examples, user interface 406 also includes audio circuitry for providing audible instructions or sounds to patient 14 and/or receiving voice commands from patient 14, which may be useful if patient 14 has limited motor functions. Patient 14, a clinician or another user may also interact with external device 21 to manually select therapy programs, generate new therapy programs, modify therapy programs through individual or global adjustments, and transmit the new programs to PCD 110, IPD 16, and/or ICD 9.

In some examples, at least some of the control of therapy delivery by PCD 110, ICD 9, and/or IPD 16 may be implemented by processing circuitry 400 of external device 21. For example, in some examples, processing circuitry 400 may control delivery of ATP therapy by PCD 110, ICD 9, and/or IPD 16 by communicating with by PCD 110, ICD 9, and/or IPD 16 and may receive data regarding sensed signals and by communicating with by PCD 110, ICM 300, ICD 9, and/or IPD 16 to control therapy delivery circuitry of any of by PCD 110, ICD 9, and/or IPD 16. In some examples, memory 402 may store ATP therapy parameters 276, may use the parameters to control therapy delivery circuitry of by PCD 110, ICD 9, and/or IPD 16, and/or may modify ATP therapy parameters 276.

Memory 402 may include instructions for operating user interface 406 and communication circuitry 408, and for managing power source 404. Memory 402 may also store any therapy data retrieved from PCD 110 during the course of therapy. The clinician may use this therapy data to determine the progression of the patient condition in order to predict future treatment. Memory 402 may include any volatile or nonvolatile memory, such as RAM, ROM, EEPROM or flash memory. Memory 402 may also include a removable memory portion that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow sensitive patient data to be removed before external device 21 is used by a different patient. In some examples, memory 402 may store ATP therapy parameters 276.

Wireless telemetry in external device 21 may be accomplished by RF communication or proximal inductive interaction of external device 21 with PCD 110, ICM 300, ICD 9, and/or IPD 16. This wireless communication is possible through the use of communication circuitry 408, which may communicate with a proprietary protocol or industry-standard protocol such as using the Bluetooth specification set. Accordingly, communication circuitry 408 may be similar to the communication circuitry contained within by PCD 110, ICD 9, and/or IPD 16. In alternative examples, external device 21 may be capable of infrared communication or direct communication through a wired connection. In this manner, other external devices may be capable of communicating with external device 21 without needing to establish a secure wireless connection.

Power source 404 may deliver operating power to the components of external device 21. Power source 404 may include a battery and a power generation circuit to produce the operating power. In some examples, the battery may be rechargeable to allow extended operation. Recharging may be accomplished by electrically coupling power source 308 to a cradle or plug that is connected to an alternating current (AC) outlet. In addition, recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within external device 21. In other examples, traditional batteries (e.g., nickel cadmium or lithium ion batteries) may be used. In addition, external device 21 may be directly coupled to an alternating current outlet to operate. Power source 404 may include circuitry to monitor power remaining within a battery. In this manner, user interface 406 may provide a current battery level indicator or low battery level indicator when the battery needs to be replaced or recharged. In some cases, power source 404 may be capable of estimating the remaining time of operation using the current battery.

According to the techniques of this disclosure, external device 21 may be used to facilitate delivery and modification of ATP therapy with one or more of the devices described in this disclosure. For example, external device 21 may help to coordinate communication between devices and/or may be used to allow a user to observe and/or influence the ATP therapy delivery and modification.

FIG. 8 is a functional block diagram illustrating an example configuration of pacemaker/cardioverter/defibrillator (PCD) 110 of the implantable medical device system of FIG. 3. As illustrated in FIG. 8, in one example, PCD 110 includes sensing circuitry 422, therapy delivery circuitry 420, processing circuitry 416 and associated memory 418, communication circuitry 424, and power source 426. The electronic components may receive power from power source 426, which may be a rechargeable or non-rechargeable battery. In other examples, PCD 110 may include more or fewer electronic components. The described circuitry may be implemented together on a common hardware component or separately as discrete but interoperable hardware or software components. Depiction of different features as circuitry is intended to highlight different functional aspects and does not necessarily imply that such circuitry must be realized by separate hardware or software components. Rather, functionality associated with one or more circuitry may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

Sensing circuitry 422 receives cardiac electrical signals from electrodes 112, 122, 124, 126, 128, 142 and 144 carried by the ventricular lead 120 and atrial lead 121, along with housing electrode 112 associated with the housing 112, for sensing cardiac events attendant to the depolarization of myocardial tissue, e.g. P-waves and R-waves. Sensing circuitry 422 may also be configured to sense fiducial points and QRS complexes. Sensing circuitry 422 may include a switch circuitry for selectively coupling electrodes 122, 124, 126, 128, 142, 144, and housing electrode 112 to sensing circuitry 422 in order to monitor electrical activity of heart 116. The switch circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple one or more of the electrodes to sensing circuitry 422. In some examples, processing circuitry 416 selects the electrodes to function as sense electrodes, or the sensing vector, via the switch circuitry within sensing circuitry 422.

According to the techniques of this disclosure, processing circuitry 416 may control an electrode to pace a heart of a patient. Processing circuitry 416 may determine a first feature, such as a fiducial point, in a local electrogram. For example, sensing circuitry 422 may sense a signal between a tip electrode and a ring electrode and processing circuitry 416 may determine the first feature in the sensed signal. Processing circuitry 416 may also determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective second feature, such as a QRS onset, in a respective electrogram. For example, sensing circuitry 422 may sense a signal between electrodes and processing circuitry 416 may determine a respective second feature. Processing circuitry 416 may determine, for each electrode of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and a respective second feature. Processing circuitry 416 may compare the respective propagation times associated with each electrode of the plurality of other electrodes. Processing circuitry 416 may determine, based on the comparison, an electrode associated with a shortest propagation time. Processing circuitry 416 may select the electrode associated with the shortest propagation time for delivery of the ATP therapy. Processing circuitry 416 may control therapy delivery circuitry 420 to deliver the ATP therapy via the selected electrode. For example, processing circuitry 416 may use a switch to select the electrode to deliver the ATP therapy.

Sensing circuitry 422 may include multiple sensing channels, each of which may be selectively coupled to respective combinations of electrodes 122, 124, 126, 128, 142, 144 and housing 112 to detect electrical activity of a particular chamber of heart 116, e.g. an atrial sensing channel and a ventricular sensing channel. Each sensing channel may comprise a sense amplifier that outputs an indication to processing circuitry 416 in response to sensing of a cardiac depolarization, in the respective chamber of heart 116. In this manner, processing circuitry 416 may receive sense event signals corresponding to the occurrence of sensed R-waves and P-waves in the respective chambers of heart 116. Sensing circuitry 422 may further include digital signal processing circuitry for providing processing circuitry 416 with digitized electrogram signals, which may be used for cardiac rhythm discrimination.

The components of sensing circuitry 422 may be analog components, digital components or a combination thereof. Sensing circuitry 422 may, for example, include one or more sense amplifiers, filters, rectifiers, threshold detectors, analog-to-digital converters (ADCs) or the like. Sensing circuitry 422 may convert the sensed signals to digital form and provide the digital signals to processing circuitry 416 for processing or analysis. For example, sensing circuitry 422 may amplify signals from the sensing electrodes and convert the amplified signals to multi-bit digital signals by an ADC. Sensing circuitry 422 may also compare processed signals to a threshold to detect the existence of atrial or ventricular depolarizations (e.g., P- or R-waves) and indicate the existence of the atrial depolarization (e.g., P-waves) or ventricular depolarizations (e.g., R-waves) to processing circuitry 416.

Sensing circuitry 422 and/or processing circuitry 416 may also include circuitry for measuring the capture threshold for the delivery of pacing pulses via electrodes 122, 124, 126, 128, 142, 144, and 112. The capture threshold may indicate the voltage and pulse width necessary to induce depolarization of the surrounding cardiac muscle. For example, processing circuitry 416 may periodically control therapy delivery circuitry 420 to modify the amplitude of pacing pulses delivered to a patient, and sensing circuitry 422 and/or processing circuitry 416 may detect whether the surrounding cardiac tissue depolarized in response to the pacing pulses, i.e., detected whether there was an evoked response to the pacing pulse. Processing circuitry 416 may determine the capture threshold based on the amplitude where loss of capture occurred. In addition to detecting and identifying specific types of cardiac rhythms, sensing circuitry 422 may also sample the detected intrinsic signals to generate an electrogram or other time-based indication of cardiac events.

Processing circuitry 416 may process the signals from sensing circuitry 422 to monitor electrical activity of the heart of the patient. Processing circuitry 416 may store signals obtained by sensing circuitry 422 as well as any generated electrogram waveforms, marker channel data or other data derived based on the sensed signals in memory 418. Processing circuitry 416 may analyze the electrogram waveforms and/or marker channel data to detect cardiac events (e.g., tachycardia). In response to detecting the cardiac event, processing circuitry 416 may control therapy delivery circuitry 420 to deliver the desired therapy to treat the cardiac event, e.g., ATP therapy.

In examples in which PCD 110 includes more than two electrodes, therapy delivery circuitry 420 may include a switch and processing circuitry 416 may use the switch to select, e.g., via a data/address bus, which of the available electrodes are used to deliver pacing pulses. The switch may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes. Processing circuitry 416 may select the electrodes to function as signal electrodes, or the signal vector, via the switch circuitry within therapy delivery circuitry 420. In some instances, the same switch circuitry may be used by both therapy delivery circuitry 420 and sensing circuitry 422. In other instances, each of sensing circuitry 422 and therapy delivery circuitry 420 may have separate switch circuitry.

Memory 418 may include computer-readable instructions that, when executed by processing circuitry 416, cause PCD 110 to perform various functions attributed throughout this disclosure to PCD 110 and processing circuitry 416. The computer-readable instructions may be encoded within memory 418. Memory 418 may comprise computer-readable storage media including any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media.

Processing circuitry 416 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry or state machine. In some examples, processing circuitry 416 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry or state machines. The functions attributed to processing circuitry 416 herein may be embodied as software, firmware, hardware or any combination thereof.

Therapy delivery circuitry 420 is electrically coupled to electrodes 122, 124, 126, 128, 142, 144, and 112. In the illustrated example, therapy delivery circuitry 420 is configured to generate and deliver electrical stimulation therapy to a heart of a patient. For example, therapy delivery circuitry 420 may deliver the electrical stimulation therapy to a portion of cardiac muscle within the heart via any combination of electrodes 122, 124, 126, 128, 142, 144, and 112. In some examples, therapy delivery circuitry 420 may deliver pacing stimulation, e.g., ATP therapy, in the form of voltage or current electrical pulses. In other examples, therapy delivery circuitry 420 may deliver stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

Although PCD 110 is generally described as delivering pacing pulses, PCD 110 may deliver cardioversion or defibrillation pulses in other examples. Therapy delivery circuitry 420 may include one or more pulse generators, capacitors, and/or other components capable of generating and/or storing energy to deliver as pacing therapy, defibrillation therapy, cardioversion therapy, cardiac resynchronization therapy, other therapy or a combination of therapies. In some instances, therapy delivery circuitry 420 may include a first set of components configured to provide pacing therapy and a second set of components configured to provide defibrillation therapy. In other instances, therapy delivery circuitry 420 may utilize the same set of components to provide both pacing and defibrillation therapy. In still other instances, therapy delivery circuitry 420 may share some of the defibrillation and pacing therapy components while using other components solely for defibrillation or pacing.

Processing circuitry 416 may control therapy delivery circuitry 420 to deliver electrical stimulation therapy, e.g., anti-tachyarrhythmia therapy, post-shock pacing, etc., to heart 116 according to therapy parameters, which may be stored in memory 418. Therapy delivery circuitry 420 is electrically coupled to electrodes 122, 124, 126, 128, 142, 144 and housing electrode 112 (all of which are shown in FIGS. 3 and 8). Therapy delivery circuitry 420 is configured to generate and deliver electrical stimulation therapy to heart 116 via selected combinations of electrodes 122, 124, 126, 128, 142, 144, and housing electrode 112.

Processing circuitry 416 may control therapy delivery circuitry 420 to deliver pacing pulses for ATP therapy according to ATP parameters 276 stored in memory 418. ATP therapy parameters 276 may include pulse intervals, pulse width, current and/or voltage amplitudes, and durations for each pacing mode. In some examples, ATP parameters 276 may include a plurality of ranges of propagation times and associated number of pulses of an ATP train, a formula that may be applied to a first propagation time, a linear equation that may be applied to a first propagation time, a continuous function that may be applied to a first propagation time, or a look-up table that may include first propagation times and associated numbers of pulses of an ATP train. For example, the pulse interval may be based on a fraction of the detected ventricular tachycardia (VT) cycle length and be between approximately 150 milliseconds and 500 milliseconds (e.g., between approximately 2.0 hertz and 7.0 hertz), and the pulse width may be between approximately 0.5 milliseconds and 2.0 milliseconds. The amplitude of each pacing pulse may be between approximately 2.0 volts and 10.0 volts. In some examples, the pulse amplitude may be approximately 6.0 V and the pulse width may be approximately 1.5 milliseconds; another example may include pulse amplitudes of approximately 5.0 V and pulse widths of approximately 1.0 milliseconds.

Each train of pulses during ATP may last for a duration of between approximately 70 milliseconds to approximately 15 seconds or be defined as a specific number of pulses. According to the techniques of this disclosure, processing circuitry 416 of PCD 110 may determine the length or duration of an ATP train, such as the first ATP train during a VT event. For example, processing circuitry 416 may determine a first feature, such as a fiducial point, in a local electrogram. Processing circuitry 416 may determine a second feature, such as a QRS onset, in a far-field electrogram. Processing circuitry 416 may determine a first propagation time based on the first feature and the second feature. Processing circuitry 416 may determine a number of pulses of the ATP train to achieve a second propagation time based on the first propagation time. Processing circuitry 416 may control therapy delivery circuitry 420 to deliver the ATP train of at least the number of pulses.

Each pulse, or burst of pulses, may include a ramp up in amplitude or in pulse rate. In addition, trains of pulses in successive ATP periods may be delivered at increasing pulse rate in an attempt to capture the heart and terminate the tachycardia.

Processing circuitry 416 controls therapy delivery circuitry 420 to generate and deliver pacing pulses with any of a number of shapes, amplitudes, pulse widths, or other characteristic to capture the heart. For example, the pacing pulses may be monophasic, biphasic, or multi-phasic (e.g., more than two phases). The pacing thresholds of the heart when delivering pacing pulses may depend upon a number of factors, including location, type, size, orientation, and/or spacing of PCD 110 and/or electrodes 122, 124, 126, 128, 142, 144, and 122, physical abnormalities of the heart (e.g., pericardial adhesions or myocardial infarctions), or other factor(s).

In examples in which PCD 110 includes more than two electrodes, therapy delivery circuitry 420 may include a switch and processing circuitry 416 may use the switch to select, e.g., via a data/address bus, which of the available electrodes are used to deliver pacing pulses. The switch may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

Memory 418 stores ATP therapy parameters 276, including intervals, counters, or other data used by processing circuitry 416 to control the delivery of pacing pulses by therapy delivery circuitry 420. Such data may include intervals and counters used by processing circuitry 416 to control the delivery of pacing pulses to heart 116. The intervals and/or counters are, in some examples, used by processing circuitry 416 to control the timing of delivery of pacing pulses relative to an intrinsic or paced event in another chamber. ATP therapy parameters 276 may also include intervals for controlling cardiac sensing functions such as blanking intervals and refractory sensing intervals and counters for counting sensed events for detecting cardiac rhythm episodes. Events sensed by sense amplifiers included in sensing circuitry 422 are identified in part based on their occurrence outside a blanking interval and inside or outside of a refractory sensing interval. Events that occur within predetermined interval ranges are counted for detecting cardiac rhythms. According to examples described herein, sensing circuitry 422, memory 418, and processing circuitry 416 are configured to use timers and counters for measuring sensed event intervals and determining event patterns for use in detecting possible ventricular lead dislodgement.

Memory 418 may be further configured to store sensed and detected data, and any other information related to the therapy and treatment of a patient. In the example of FIG. 8, memory 418 may store sensed ECGs, detected arrhythmias, communications from PCD 100. In other examples, memory 418 may act as a temporary buffer for storing data until it can be uploaded to another implanted device, or external device 21.

Communication circuitry 424 is used to communicate with external device 21 and/or ICM 300 for transmitting data accumulated by PCD 110 and for receiving interrogation and programming commands to and/or from external device 21 and/or ICM 300. Communication circuitry 268 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 21 (FIGS. 1A-1C and 7), ICM 300 (FIGS. 3 and 9), a clinician programmer, a patient monitoring device, or the like. For example, communication circuitry 424 may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifier components for transmission and reception of data. Under the control of processing circuitry 416, communication circuitry 424 may receive downlink telemetry from and send uplink telemetry to external device 21 with the aid of an antenna, which may be internal and/or external. Processing circuitry 416 may provide the data to be uplinked to external device 21 and the control signals for the telemetry circuit within communication circuitry 424, e.g., via an address/data bus. In some examples, communication circuitry 424 may provide received data to processing circuitry 416 via a multiplexer.

In some examples, PCD 110 may signal external device 21 to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic plc, of Dublin, Ireland, or some other network linking a patient to a clinician. PCD 110 may spontaneously transmit information to the network or in response to an interrogation request from a user.

Power source 426 may be any type of device that is configured to hold a charge to operate the circuitry of PCD 110. Power source 426 may be provided as a rechargeable or non-rechargeable battery. In other example, power source 426 may incorporate an energy scavenging system that stores electrical energy from movement of PCD 110 within patient 114.

The various circuitry of PCD 110 may include any one or more processors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or equivalent discrete or integrated circuitry, including analog circuitry, digital circuitry, or logic circuitry.

According to the techniques of this disclosure, PCD 110 may determine a first feature, such as a fiducial point, in a local electrogram, determine a second feature, such as a QRS onset, in a far-field electrogram, determine a first propagation time based on the first feature and the second feature, determine, based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and deliver the ATP train of at least the number of pulses.

According to the techniques of this disclosure, PCD 110 may control an electrode to pace a heart of a patient, determine a first feature, such as a fiducial point, in a local electrogram, determine, for each electrode of a plurality of other electrodes communicatively coupled to a medical device system (which may include PCD 110), a respective propagation time based on the first feature and a respective second feature, in a respective electrogram, compare the respective propagation times associated with each electrode, determine, based on the comparison, an electrode associated with a shortest propagation time, and select the electrode associated with the shortest propagation time for delivery of the ATP therapy. Therapy delivery circuitry of PCD 110 may deliver the ATP therapy via the selected electrode.

FIG. 9 is a functional block diagram illustrating an example configuration of ICM 300 of FIGS. 1A-1C and FIG. 4. In the illustrated example, ICM 300 includes processing circuitry 1000, memory 1002, sensing circuitry 1006, communication circuitry 1008 connected to antenna 322, and power source 1010. The electronic components may receive power from a power source 1010, which may be a rechargeable or non-rechargeable battery. In other examples, ICM 300 may include more or fewer electronic components. The described circuitry may be implemented together on a common hardware component or separately as discrete but interoperable hardware or software components. Depiction of different features as circuitry is intended to highlight different functional aspects and does not necessarily imply that such circuitry must be realized by separate hardware or software components. Rather, functionality associated with one or more circuitry may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

Memory 1002 includes computer-readable instructions that, when executed by processing circuitry 1000, cause ICM 300 and processing circuitry 1000 to perform various functions attributed to ICM 300 and processing circuitry 1000 herein. Memory 1002 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processing circuitry 1002 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 100 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 1000 herein may be embodied as software, firmware, hardware or any combination thereof.

Processing circuitry 1000 controls sensing circuitry 1006 to sense evoked responses of the heart via electrodes 304 and 306. Although ICM 300 may only include two electrodes, e.g., electrodes 304 and 306, ICM 300 may utilize three or more electrodes in other examples. ICM 300 may use any combination of electrodes to detect electrical signals from patient 114. Sensing circuitry 1006 is electrically coupled to electrodes 304 and 306 carried on housing 302 of ICM 300.

Sensing circuitry 1006 is electrically connected to and monitors signals from one or more of electrodes 304 and 306 in order to monitor electrical activity of a heart, impedance, or other electrical phenomenon. Sensing may be done to determine heart rates or heart rate variability, or to detect arrhythmias (e.g., tachyarrhythmias or bradycardia) or other electrical signals. Sensing circuitry 1004 may also include a switch to select which of the available electrodes (or electrode polarity) are used to sense the heart activity, depending upon which electrode combination, or electrode vector, is used in the current sensing configuration. In examples with several electrodes, processing circuitry 1000 may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch circuitry within sensing circuitry 1004. Sensing circuitry 1004 may include one or more detection channels, each of which may be coupled to a selected electrode configuration for detection of cardiac signals via that electrode configuration. Some detection channels may be configured to detect cardiac events, such as fiducial points, QRS complexes, P- or R-waves, and provide indications of the occurrences of such events to processing circuitry 1000 Processing circuitry 1000 may control the functionality of sensing circuitry 1006 by providing signals via a data/address bus.

The components of sensing circuitry 1006 may be analog components, digital components or a combination thereof. Sensing circuitry 1006 may, for example, include one or more sense amplifiers, filters, rectifiers, threshold detectors, analog-to-digital converters (ADCs) or the like. Sensing circuitry 1006 may convert the sensed signals to digital form and provide the digital signals to processing circuitry 1000 for processing or analysis. For example, sensing circuitry 1006 may amplify signals from the sensing electrodes and convert the amplified signals to multi-bit digital signals by an ADC. Sensing circuitry 1006 may also compare processed signals to a threshold to detect the existence of atrial or ventricular depolarizations (e.g., P- or R-waves) and indicate the existence of the atrial depolarization (e.g., P-waves) or ventricular depolarizations (e.g., R-waves) to processing circuitry 1000.

Processing circuitry 1000 may implement programmable counters and may withhold sensing from one or more channels of sensing circuitry 1006 for a time interval during and after delivery of electrical stimulation to heart 116. The durations of these intervals may be determined by processing circuitry 1000 in response to stored data in memory 1002.

Interval counters implemented by processing circuitry 1000 may be reset upon sensing of R-waves and P-waves with detection channels of sensing circuitry 1006. The value of the count present in the interval counters when reset by sensed R-waves and P-waves may be used by processing circuitry 1000 to measure the durations of R-R intervals, P-P intervals, P-R intervals and R-P intervals, which are measurements that may be stored in memory 1002. Processing circuitry 1000 may use the count in the interval counters to detect a tachyarrhythmia event, such as atrial fibrillation (AF), atrial tachycardia (AT), VF, or VT. These intervals may also be used to detect the overall heart rate, ventricular contraction rate, and heart rate variability. A portion of memory 1002 may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by processing circuitry 1000 in response to the occurrence of a sense interrupt to determine whether the patient's heart 116 is presently exhibiting atrial or ventricular tachyarrhythmia.

In some examples, an arrhythmia detection method may include any suitable tachyarrhythmia detection algorithms. In some examples, methodologies that utilize timing and morphology of the electrocardiogram, may be employed by processing circuitry 1000 in other examples.

In some examples, processing circuitry 1000 may determine that tachyarrhythmia has occurred by identification of shortened R-R (or P-P) interval lengths. Generally, processing circuitry 1000 detects tachycardia when the interval length falls below 220 milliseconds and fibrillation when the interval length falls below 180 milliseconds. In other examples, processing circuitry 1000 may detect ventricular tachycardia when the interval length falls between 330 milliseconds and ventricular fibrillation when the interval length falls below 240 milliseconds. These interval lengths are merely examples, and a user may define the interval lengths as desired, which may then be stored within memory 1002. This interval length may need to be detected for a certain number of consecutive cycles, for a certain percentage of cycles within a running window, or a running average for a certain number of cardiac cycles, as examples. In other examples, additional physiological parameters may be used to detect an arrhythmia. For example, processing circuitry 1000 may analyze one or more morphology measurements, impedances, or any other physiological measurements to determine that patient 114 is experiencing a tachyarrhythmia.

In addition to detecting and identifying specific types of cardiac rhythms, sensing circuitry 1004 may also sample the detected intrinsic signals to generate an electrogram or other time-based indication of cardiac events. Processing circuitry 1000 may also be able to coordinate the delivery of pacing pulses from another device, such as PCD 110. For example, processing circuitry 1000 may identify delivered pulses from PCD 110 via sensing circuitry 1006 and update pulse timing to accomplish a selected pacing regimen. This detection may be on a pulse-to-pulse or beat-to-beat basis, or on a less frequent basis to make slight modifications to pulse rate over time. In other examples, IPDs may communicate with each other via communication circuitry 1008 and/or instructions over a carrier wave (such as a stimulation waveform). In this manner, ATP pacing may be coordinated by multiple devices.

Memory 1002 may be configured to store a variety of sensed and detected data and any other information related to the therapy and treatment of patient 114. In the example of FIG. 9, memory 1002 may store sensed ECGs and/or detected arrhythmias, communications from PCD 110. In other examples, memory 1002 may act as a temporary buffer for storing data until it can be uploaded to PCD 110, another implanted device, or external device 21.

Communication circuitry 1008 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 21, PCD 110 (FIGS. 1A-1C), a clinician programmer, a patient monitoring device, or the like. For example, communication circuitry 1008 may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifier components for transmission and reception of data. Under the control of processing circuitry 1000, communication circuitry 1008 may receive downlink telemetry from and send uplink telemetry to external device 21 with the aid of antenna 322, which may be internal and/or external. Processing circuitry 100 may provide the data to be uplinked to external device 21 and the control signals for the telemetry circuit within communication circuitry 1008, e.g., via an address/data bus. In some examples, communication circuitry 1008 may provide received data to processing circuitry 1000 via a multiplexer.

In some examples, ICM 300 may signal external device 21 to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic plc., of Dublin, Ireland, or some other network linking patient 114 to a clinician. ICM 300 may spontaneously transmit information to the network or in response to an interrogation request from a user.

Power source 1010 may be any type of device that is configured to hold a charge to operate the circuitry of ICM 300. Power source 1010 may be provided as a rechargeable or non-rechargeable battery. In other example, power source 1010 may incorporate an energy scavenging system that stores electrical energy from movement of ICM 200 within patient 114.

The various circuitry of IPD 16 may include any one or more processors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or equivalent discrete or integrated circuitry, including analog circuitry, digital circuitry, or logic circuitry.

PCD 110 may deliver ATP therapy and sense evoked response(s) at one or more locations and ICM 300 may sense evoked response(s) at one or more different locations via sensing circuitry 1006. The evoked response(s) may be detected as described above with reference to FIG. 5.

FIGS. 10A-10C are conceptual diagrams illustrating example local electrograms and far-field electrograms according to the techniques of this disclosure. These examples depict how activation times within far-field QRS may vary from patient to patient, or from time to time within the same patient. A longer activation time suggests that a greater number of pulses may be needed in an ATP pulse train to reach a VT circuit. In each of FIGS. 10A-10C, the top electrogram is a local electrogram and the bottom electrogram is a far-field electrogram. For example, the local electrogram may be measured from a tip to a ring of a local electrode. The far-field electrogram may be measured from a coil to can.

In the example of FIG. 10A, a fiducial point 504 in local electrogram 500 is precedes a QRS onset in far-field electrogram 502. In this example, there is approximately a 20 milliseconds propagation time from fiducial point 504 to the QRS onset in far-field electrogram 502.

In the example of FIG. 10B, a fiducial point 510 in local electrogram 506 precedes a QRS onset in far-field electrogram 508. In this example, there is approximately a 50 milliseconds propagation time from fiducial point 510 to the QRS onset in far-field electrogram 508.

In FIG. 10C, a fiducial point 516 in local electrogram 512 is shown compared to a QRS onset in far-field electrogram 514. In this example, there is approximately a 130 milliseconds propagation time from fiducial point 516 to the QRS onset in far-field electrogram 514.

FIG. 11 is a conceptual diagram illustrating an ATP train. ATP train 428 is shown beginning at time 430A which may be the time that the ATP therapy is initiated and a first pulse of ATP train 428 is delivered. Time 430B may indicate a time at which a second pulse of ATP train 428 is delivered. Any suitable time interval may separate time 430A and time 430B. In the illustrated example, the time separating time 430A and time 430B is noted as T_(s1). In ATP train 428, a plurality of pulses may be delivered at times 430A, 430B, 430C, 430D, 430F, and 430G. Each subsequently delivered pulse may be separated by substantially the same time interval of T_(s1). In some examples, the number of pulses in ATP train 432 may be sufficient to achieve a second propagation time of 100 milliseconds long, 150 milliseconds long, or 210 milliseconds long. In some examples, processing circuitry of a medical device system may determine the number of pulses of ATP train 432 based on a determination of which of a plurality of propagation time ranges a first propagation time is associated with. In other examples, processing circuitry of a medical device system may determine the number of pulses of ATP train 432 based on application of a formula, a linear equation, or a continuous function to a first propagation time. In other examples, processing circuitry of a medical device system may determine the number of pulses of ATP train 432 by looking up a first propagation time in a look-up table.

FIG. 12 is a flowchart illustrating an example determinization of a length of an ATP train according to the techniques of this disclosure. A medical device system, which may include any of or a combination of ICD 9, IPD 16, or PCD 110, may determine a first feature, such as a fiducial point (e.g., an activation point), in a local electrogram (560). For example, the medical device system may sense a local R-wave or other feature using a tip to ring electrode (e.g., electrode 122 to electrode 124) using any known techniques. A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may determine a second feature, such as a QRS onset, in a far-field electrogram (562). For example, the medical device system may sense the onset of a QRS complex (or features of the QRS complex, such as max slope, max amp, or R-wave) using a can to coil electrode (e.g., electrode 142 or electrode 144 to housing electrode 112) using any known techniques. A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may determine a first propagation time based on the first feature and the second feature (564). For example, the medical device system may subtract a time at which the first feature was sensed from a time at which the second feature was sensed to determine the first propagation time.

A medical device system, such as any of or any combination of ICD 9, IPD 16, or PCD 110, may determine, based on the first propagation time, a number of pulses of an ATP train to achieve a second propagation time (566). For example, the medical device system may determine a range associated with the first propagation time. For example, the medical device system may determine whether the first propagation time is less than 10 milliseconds, whether the first propagation time is between 10 milliseconds and 40 milliseconds; or whether the first propagation time is more than 40 milliseconds. If the first propagation time is less than 10 milliseconds, the medical device system may determine the second propagation time to be 100 milliseconds. If the propagation time is between 10 milliseconds and 40 milliseconds, the medical device system may determine the second propagation time to be 150 ms. If the propagation time is more 40 milliseconds, the medical device system may determine the second propagation time to be 210 milliseconds.

In other examples, the medical device system may determine the number of pulses by applying a formula to the first propagation time. In some examples, the medical device system may determine the number of pulses by applying a linear equation to the first propagation time. In some examples, the medical device system may determine the number of pulses by applying a continuous function to the first propagation time. In some examples, the medical device system may determine the number of pulses by looking up the first propagation time in a look-up table.

A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may deliver the ATP train of at least the number of pulses (568). For example, therapy delivery circuitry of the medical device system may deliver via one or more electrodes an ATP train having of at least the number of pulses. For example, if the second propagation time is 100 milliseconds, the therapy delivery circuitry may deliver an ATP train of at least a number of pulses to achieve a second propagation time of 100 milliseconds. In some examples, the ATP train is a first ATP train delivered during a VT event.

FIG. 13 is a flowchart illustrating an example determinization of an electrode to deliver ATP therapy according to the techniques of this disclosure. A medical device system, which may include any of or a combination of ICD 9, IPD 16, or PCD 110, may control an electrode to pace the heart of a patient (569). For example, therapy delivery circuitry of the medical device system may control the electrode to pace the heart of the patient. The medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may determine a first feature, such as a fiducial point (e.g., an activation point), in a local electrogram (570). For example, the medical device system may sense a local fiducial point using a tip electrode to ring electrode (e.g., electrode 122 to electrode 124). A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, such as one or more of electrodes 130 or 132 of left ventricle lead 120, a second feature, such as a QRS onset, in a respective far-field electrogram (572). A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may determine, for each electrode of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the respective second feature (574). For example, for each respective electrode of the plurality of other electrodes communicatively coupled to the medical device system, the medical device system may subtract a time at which the first feature was sensed from a time at which the respective second feature was sensed to determine the respective propagation time. A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may compare the respective propagation times associated with each respective electrode of the plurality of other electrodes (576). For example, the medical device system may compare the length of each respective propagation time associated with each respective electrode. A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may determine, based on the comparison, an electrode associated with a shortest respective propagation time (578). For example, the medical device system may determine which electrode has the shortest propagation time from among all the electrodes having associated propagation times. A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may select the electrode associated with the shortest respective propagation time for delivery of ATP therapy (580). For example, the medical device system may switch switching circuitry such that the electrode associated with the shortest propagation time is coupled to the therapy delivery circuitry. A medical device system, such as any of or a combination of ICD 9, IPD 16, or PCD 110, may deliver, via the selected electrode, the ATP therapy (582). For example, the medical device system may deliver ATP therapy through therapy delivery circuitry and via the selected electrode.

Any suitable modifications may be made to the techniques described herein and any suitable device, processing circuitry, therapy delivery circuitry, and/or electrodes may be used for performing the steps of the methods described herein. The steps of the methods may be performed by any suitable number of devices. For example, a processing circuitry of one device may perform some of the steps while a therapy delivery circuitry and/or sensing circuitry of another device may perform other steps of the method, while communication circuitry may allow for communication needed for the processing circuitry to receive information from other devices. This coordination may be performed in any suitable manner according to particular needs.

The disclosure contemplates computer-readable storage media comprising instructions to cause a processor to perform any of the functions and techniques described herein. The computer-readable storage media may take the example form of any volatile, non-volatile, magnetic, optical, or electrical media, such as a RAM, ROM, NVRAM, EEPROM, or flash memory. The computer-readable storage media may be referred to as non-transitory. A programmer, such as patient programmer or clinician programmer, or other computing device may also contain a more portable removable memory type to enable easy data transfer or offline data analysis.

The techniques described in this disclosure, including those attributed to ICD 9, IPD 16, PCD 110, external device 21, and various constituent components, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in programmers, such as physician or patient programmers, stimulators, remote servers, or other devices. The term “processor” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

Such hardware, software, firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. For example, any of the techniques or processes described herein may be performed within one device or at least partially distributed amongst two or more devices, such as between ICD 9, IPD 16, PCD 110, and/or external device 21. In addition, any of the described units, circuitry or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as circuitry is intended to highlight different functional aspects and does not necessarily imply that such circuitry must be realized by separate hardware or software components. Rather, functionality associated with one or more circuitry may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

The techniques described in this disclosure may also be embodied or encoded in an article of manufacture including a non-transitory computer-readable storage medium encoded with instructions. Instructions embedded or encoded in an article of manufacture including a non-transitory computer-readable storage medium encoded, may cause one or more programmable processors, or other processors, to implement one or more of the techniques described herein, such as when instructions included or encoded in the non-transitory computer-readable storage medium are executed by the one or more processors. Example non-transitory computer-readable storage media may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magnetic media, optical media, or any other computer readable storage devices or tangible computer readable media.

As used herein, the term “circuitry” refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality.

In some examples, a computer-readable storage medium comprises non-transitory medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache).

This disclosure includes the following non-limiting examples.

Example 1. A method comprising: determining, by a medical device system, a first feature in a local electrogram; determining, by the medical device system, a second feature in a far-field electrogram; determining, by the medical device system, a first propagation time based on the first feature and the second feature; determining, by the medical device system and based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and delivering, by the medical device system, the ATP train of at least the number of pulses.

Example 2. The method of example 1, wherein the first feature is an activation point.

Example 3. The method of example 1 or example 2, wherein the second feature is a QRS onset.

Example 4. The method of any combination of examples 1-3, wherein determining the number of pulses comprises: determining which of a plurality of propagation time ranges is associated with the first propagation time; and selecting, based on the determined range, one of a plurality of numbers of pulses.

Example 5. The method of example 4, wherein determining which of the plurality of propagation time ranges is associated with the propagation time comprises at least one of: determining whether the propagation time is less than 10 milliseconds; determining whether the propagation time is between 10 milliseconds and 40 milliseconds; or determining whether the propagation time is more than 40 milliseconds.

Example 6. The method of example 5, wherein the first propagation time is less than 10 milliseconds and the second propagation time is 100 milliseconds.

Example 7. The method of example 5, wherein the first propagation time is between 10 milliseconds and 40 milliseconds, and the second propagation time is 150 milliseconds.

Example 8. The method of example 5, wherein the first propagation time is more than 40 milliseconds and the second propagation time is 210 milliseconds.

Example 9. The method of any combination of examples 1-8, wherein determining the number of pulses to achieve the second propagation time comprises applying a formula to the first propagation time.

Example 10. The method of any combination of examples 1-8, wherein determining the number of pulses to achieve the second propagation time comprises applying a linear equation to the first propagation time.

Example 11. The method of any combination of examples 1-8, wherein determining the number of pulses to achieve the second propagation time comprises applying a continuous function to the first propagation time.

Example 12. The method of any combination of examples 1-8, wherein determining the number of pulses to achieve the second propagation time comprises looking up the first propagation time in a look-up table.

Example 13. The method of any combination of examples 1-12, wherein the ATP train is a first ATP train delivered during a ventricular tachycardia event.

Example 14. A method comprising: pacing, by a first electrode, a heart of a patient; determining, by a medical device system, a first feature in a local electrogram in response to the pace; determining, by the medical device system and for each electrode of a plurality of other electrodes communicatively coupled to a medical device, a respective second feature in a respective electrogram; determining, by the medical device system, and for each of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the respective second feature onset; comparing, by the medical device system, the respective propagation times associated with each of the plurality of other electrodes; determining, by the medical device system and based on the comparison, an electrode associated with a shortest respective propagation time; selecting, by the medical device system, the electrode associated with the shortest respective propagation time for delivery of anti-tachycardia pacing (ATP) therapy; and delivering, by the medical device system and via the selected electrode, the ATP therapy.

Example 15. The method of example 14, wherein the first feature is an activation point.

Example 16. The method of example 14 or example 15, wherein the second feature is a QRS onset.

Example 17. A medical device system comprising: therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry, the ATP therapy comprising an ATP train; and processing circuitry configured to: determine a first feature in a local electrogram; determine a second feature in a far-field electrogram; determine a first propagation time based on the first feature and the second feature; determine a number of pulses of the ATP train to achieve a second propagation time based on the first propagation time; and control the therapy delivery circuitry to deliver the ATP train of at least the number of pulses.

Example 18. The medical device system of example 17, wherein the first feature is an activation point.

Example 19. The medical device system of example 17 or example 18, wherein the second feature is a QRS onset.

Example 20. The medical device system of any combination of examples 17-19, wherein, as part of determining the number of pulses, the processing circuitry is configured to: determine a range associated with the first propagation time; and select, based on the determined range, one of the plurality of numbers of pulses.

Example 21. The medical device system of example 20, wherein, as part of determining the range associated with the first propagation time, the processing circuitry is configured to determine at least one of: whether the first propagation time is less than 10 milliseconds; whether the first propagation time is between 10 milliseconds and 40 milliseconds; or whether the first propagation time is more than 40 milliseconds.

Example 22. The medical device system of example 21, wherein the first propagation time is less than 10 milliseconds and the second propagation time is 100 milliseconds.

Example 23. The medical device system of example 21, wherein the first propagation time is between 10 milliseconds and 40 milliseconds and the second propagation time is 150 milliseconds.

Example 24. The medical device system of example 21, wherein the first propagation time is more 40 milliseconds and the second propagation time is 210 milliseconds.

Example 25. The medical device system of any combination of examples 17-24, wherein, as part of determining the number of pulses to achieve the second propagation time, the processing circuitry is configured to apply a formula to the first propagation time.

Example 26. The medical device system of any combination of examples 17-24, wherein, as part of determining the number of pulses to achieve the second propagation time, the processing circuitry is configured to apply a linear equation to the first propagation time.

Example 27. The medical device system of any combination of examples 17-24, wherein, as part of determining the number of pulses to achieve the second propagation time, the processing circuitry is configured to apply a continuous function to the first propagation time.

Example 28. The medical device system of any combination of examples 17-24, wherein, as part of determining the number of pulses to achieve the second propagation time, the processing circuitry is configured to look up the first propagation time in a look-up table.

Example 29. The medical device system of any combination of examples 17-28, wherein the ATP train is a first ATP train delivered during a ventricular tachycardia event.

Example 30. The medical device system of any combination of examples, 17-29, wherein the processing circuitry is further configured to: control a first electrode to pace a heart of a patient; determine a third feature in a local electrogram in response to the pace; determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective fourth feature in a respective electrogram; determine, for each of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the third feature and the respective fourth feature; compare the respective propagation times associated with each of the plurality of other electrodes; determine, based on the comparison, an electrode associated with a shortest respective propagation time; select the electrode associated with the shortest respective propagation time for delivery of the ATP therapy; and control the therapy delivery circuitry to deliver the ATP therapy via the selected electrode.

Example 31. A medical device system comprising: therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry; and processing circuitry configured to: control a first electrode to pace a heart of a patient; determine a first feature in a local electrogram in response to the pace; determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective second feature in a respective electrogram; determine, for each of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the respective second feature; compare the respective propagation times associated with each of the plurality of other electrodes; determine, based on the comparison, an electrode associated with a shortest respective propagation time; select the electrode associated with the shortest respective propagation time for delivery of the ATP therapy; and control the therapy delivery circuitry to deliver the ATP therapy via the selected electrode.

Example 32. The medical device system of example 31, wherein the first feature is an activation point.

Example 33. The medical device system of example 31 or example 32, wherein the second feature is a QRS onset.

Example 34. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause processing circuitry to: determine a first feature in a local electrogram; determine a second feature in a far-field electrogram; determine a first propagation time based on the first feature and the second feature; determine, based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and control therapy delivery circuitry to deliver the ATP train of the at least the number of pulses.

Example 35. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause processing circuitry to: determine a first feature in a local electrogram; determine, for each electrode of a plurality of other electrodes communicatively coupled to a medical device system, a respective second feature in a respective electrogram; determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the first feature and the second feature; compare the respective propagation times associated with each of a plurality of other electrodes; determine, based on the comparison, an electrode associated with a shortest respective propagation time; select the electrode associated with the shortest respective propagation time for delivery of anti-tachycardia pacing (ATP) therapy; and control therapy delivery circuitry to deliver the ATP therapy via the selected electrode.

Various examples have been described for delivering cardiac stimulation therapies as well as coordinating the operation of various devices within a patient. Any combination of the described operations or functions is contemplated. These and other examples are within the scope of the following claims. 

What is claimed is:
 1. A method comprising: determining, by a medical device system, a first feature in a local electrogram; determining, by the medical device system, a second feature in a far-field electrogram; determining, by the medical device system, a first propagation time based on the first feature and the second feature; determining, by the medical device system and based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and delivering, by the medical device system, the ATP train of at least the number of pulses.
 2. The method of claim 1, wherein the first feature is an activation point.
 3. The method of claim 1, wherein the second feature is a QRS onset.
 4. The method of claim 1, wherein determining the number of pulses comprises: determining which of a plurality of propagation time ranges is associated with the first propagation time; and selecting, based on the determined range, one of a plurality of numbers of pulses.
 5. The method of claim 4, wherein determining which of the plurality of propagation time ranges is associated with the propagation time comprises at least one of: determining whether the propagation time is less than 10 milliseconds; determining whether the propagation time is between 10 milliseconds and 40 milliseconds; or determining whether the propagation time is more than 40 milliseconds.
 6. The method of claim 5, wherein the first propagation time is less than 10 milliseconds and the second propagation time is 100 milliseconds.
 7. The method of claim 5, wherein the first propagation time is between 10 milliseconds and 40 milliseconds, and the second propagation time is 150 milliseconds.
 8. The method of claim 5, wherein the first propagation time is more than 40 milliseconds and the second propagation time is 210 milliseconds.
 9. The method of claim 1, wherein the ATP train is a first ATP train delivered during a ventricular tachycardia event.
 10. A medical device system comprising: therapy delivery circuitry configured to deliver anti-tachycardia pacing (ATP) therapy to a heart of a patient via electrodes communicatively coupled to the therapy delivery circuitry, the ATP therapy comprising an ATP train; and processing circuitry configured to: determine a first feature in a local electrogram; determine a second feature in a far-field electrogram; determine a first propagation time based on the first feature and the second feature; determine a number of pulses of the ATP train to achieve a second propagation time based on the first propagation time; and control the therapy delivery circuitry to deliver the ATP train of at least the number of pulses.
 11. The medical device system of claim 10, wherein the first feature is an activation point.
 12. The medical device system of claim 10, wherein the second feature is a QRS onset.
 13. The medical device system of claim 10, wherein, as part of determining the number of pulses, the processing circuitry is configured to: determine a range associated with the first propagation time; and select, based on the determined range, one of the plurality of numbers of pulses.
 14. The medical device system of claim 13, wherein, as part of determining the range associated with the first propagation time, the processing circuitry is configured to determine at least one of: whether the first propagation time is less than 10 milliseconds; whether the first propagation time is between 10 milliseconds and 40 milliseconds; or whether the first propagation time is more than 40 milliseconds.
 15. The medical device system of claim 14, wherein the first propagation time is less than 10 milliseconds and the second propagation time is 100 milliseconds.
 16. The medical device system of claim 14, wherein the first propagation time is between 10 milliseconds and 40 milliseconds and the second propagation time is 150 milliseconds.
 17. The medical device system of claim 14, wherein the first propagation time is more 40 milliseconds and the second propagation time is 210 milliseconds.
 18. The medical device system of claim 10, wherein the ATP train is a first ATP train delivered during a ventricular tachycardia event.
 19. The medical device system of claim 10 wherein the processing circuitry is further configured to: control a first electrode to pace a heart of a patient; determine a third feature in a local electrogram in response to the pace; determine, for each electrode of a plurality of other electrodes communicatively coupled to the medical device system, a respective fourth feature in a respective electrogram; determine, for each of the plurality of other electrodes communicatively coupled to the medical device system, a respective propagation time based on the third feature and the respective fourth feature; compare the respective propagation times associated with each of the plurality of other electrodes; determine, based on the comparison, an electrode associated with a shortest respective propagation time; select the electrode associated with the shortest respective propagation time for delivery of the ATP therapy; and control the therapy delivery circuitry to deliver the ATP therapy via the selected electrode.
 20. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause processing circuitry to: determine a first feature in a local electrogram; determine a second feature in a far-field electrogram; determine a first propagation time based on the first feature and the second feature; determine, based on the first propagation time, a number of pulses of an anti-tachycardia pacing (ATP) train to achieve a second propagation time; and control therapy delivery circuitry to deliver the ATP train of the at least the number of pulses. 